JP2023024425A - Positive electrode for nonaqueous electrolyte secondary battery, nonaqueous electrolyte secondary battery using the same, battery module, and battery system - Google Patents

Positive electrode for nonaqueous electrolyte secondary battery, nonaqueous electrolyte secondary battery using the same, battery module, and battery system Download PDF

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JP2023024425A
JP2023024425A JP2022170500A JP2022170500A JP2023024425A JP 2023024425 A JP2023024425 A JP 2023024425A JP 2022170500 A JP2022170500 A JP 2022170500A JP 2022170500 A JP2022170500 A JP 2022170500A JP 2023024425 A JP2023024425 A JP 2023024425A
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positive electrode
active material
electrode active
material layer
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輝 吉川
Teru Yoshikawa
裕一 佐飛
Yuichi Satobi
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Sekisui Chemical Co Ltd
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    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
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    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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    • H01M4/624—Electric conductive fillers
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    • H01M50/10—Primary casings, jackets or wrappings of a single cell or a single battery
    • H01M50/102—Primary casings, jackets or wrappings of a single cell or a single battery characterised by their shape or physical structure
    • H01M50/103—Primary casings, jackets or wrappings of a single cell or a single battery characterised by their shape or physical structure prismatic or rectangular
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    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/204—Racks, modules or packs for multiple batteries or multiple cells
    • H01M50/207—Racks, modules or packs for multiple batteries or multiple cells characterised by their shape
    • H01M50/209—Racks, modules or packs for multiple batteries or multiple cells characterised by their shape adapted for prismatic or rectangular cells
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    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrode for a nonaqueous electrolyte secondary battery capable of improving the rapid charge-discharge cycle characteristics of a nonaqueous electrolyte secondary battery and reducing the impedance of the nonaqueous electrolyte secondary battery while having excellent peel strength of a positive active material layer.
SOLUTION: Disclosed is a positive electrode 1 for a nonaqueous electrolyte secondary battery which has a current collector 11, and an active material layer 12 existing on the current collector. The active material layer 12 includes: a positive electrode active material; and a conductive carbon material. The content of a low resistance conductive carbon material having a resistivity of 0.10 Ω cm or less with respect to the total mass of the active material layer 12 is 0.5 mass% or less. The positive electrode 1 for the nonaqueous electrolyte secondary battery has the current collector 11 and the active material layer 12 existing on the current collector. The active material layer 12 includes the positive electrode active material. On at least a part of the surface of the positive electrode active material, an active material coating part containing a conductive material exists and the powder resistivity of the active material layer 12 is 10 to 1,000 Ω cm.
SELECTED DRAWING: Figure 1
COPYRIGHT: (C)2023,JPO&INPIT

Description

本発明は、非水電解質二次電池用正極、並びにこれを用いた非水電解質二次電池、電池モジュール、及び電池システムに関する。
本願は、２０２１年３月１９日に日本に出願された特願２０２１－０４５９７７号、２０２１年８月１８日に日本に出願された特願２０２１－１３３３８８号、及び２０２１年８月１８日に日本に出願された特願２０２１－１３３４４７号に基づき優先権を主張し、その内容をここに援用する。 TECHNICAL FIELD The present invention relates to positive electrodes for non-aqueous electrolyte secondary batteries, non-aqueous electrolyte secondary batteries, battery modules, and battery systems using the same.
This application is based on Japanese Patent Application No. 2021-045977 filed in Japan on March 19, 2021, Japanese Patent Application No. 2021-133388 filed in Japan on August 18, 2021, and Japan on August 18, 2021. The priority is claimed based on Japanese Patent Application No. 2021-133447 filed in , and the contents thereof are incorporated herein.

非水電解質二次電池は、一般的に、正極、非水電解質、負極、及び正極と負極との間に設置される分離膜（セパレータ）により構成される。
非水電解質二次電池の正極としては、リチウムイオンを含む正極活物質、導電助剤、及び結着材からなる組成物を、金属箔（集電体）の表面に固着させたものが知られている。リチウムイオンを含む正極活物質としては、コバルト酸リチウム（ＬｉＣｏＯ２）、ニッケル酸リチウム（ＬｉＮｉＯ２）、マンガン酸リチウム（ＬｉＭｎ２Ｏ４）等のリチウム遷移金属複合酸化物や、リン酸鉄リチウム（ＬｉＦｅＰＯ４）等のリチウムリン酸化合物が実用化されている。 A non-aqueous electrolyte secondary battery is generally composed of a positive electrode, a non-aqueous electrolyte, a negative electrode, and a separation membrane (separator) placed between the positive electrode and the negative electrode.
As a positive electrode for non-aqueous electrolyte secondary batteries, there is known one in which a composition comprising a positive electrode active material containing lithium ions, a conductive aid, and a binder is adhered to the surface of a metal foil (current collector). ing. Examples of positive electrode active materials containing lithium ions include lithium transition metal composite oxides such as lithium cobaltate (LiCoO 2 ), lithium nickelate (LiNiO 2 ), lithium manganate (LiMn 2 O 4 ), and lithium iron phosphate ( LiFePO 4 ) and other lithium phosphate compounds have been put to practical use.

特許文献１では、正極活物質の特性を評価する指標として、正極活物質の二次粒子の拡がり抵抗値に着目し、正極活物質の組成や製造条件を変えて前記拡がり抵抗値が異なる正極活物質を製造した例が記載されている。実施例には導電助剤であるアセチレンブラックを６質量％含む二次電池が記載されている。
特許文献２は、導電助剤として薄片状のグラフェンを用いることによって二次電池の出力特性及びエネルギー密度を向上させた実施例が記載されている。薄片状のグラフェンを用いた実施例は、正極断面を拡がり抵抗値に基づいてマッピングしたときの、特定の抵抗値以下の部分のアスペクト比が、粉末状の導電助剤を用いた比較例に比べて大きくなることが示されている。 In Patent Document 1, as an index for evaluating the characteristics of the positive electrode active material, attention is paid to the spreading resistance value of the secondary particles of the positive electrode active material. An example of how the material was produced is described. Examples describe a secondary battery containing 6% by mass of acetylene black as a conductive agent.
Patent Document 2 describes an example in which the output characteristics and energy density of a secondary battery are improved by using flaky graphene as a conductive aid. In the examples using flaky graphene, when the cross section of the positive electrode is spread and mapped based on the resistance value, the aspect ratio of the portion below a specific resistance value is higher than that in the comparative example using the powdery conductive additive. It has been shown that the

特許文献３の実施例には、集電体上に、リチウムイオンを含む正極活物質１００質量部と、導電助剤５質量部と、結着材５質量部と、増粘剤１質量部とからなる正極活物質層を設けた正極が記載されている。正極活物質の表面を炭素被覆した実施例は、炭素被覆しない比較例に比べてサイクル特性が向上したこと示されている。
特許文献４には、金属箔の表面に導電性粒子と結着材を含む被覆層を設け、その上に、電極活物質と０～１．４質量％の導電助剤を含む電極合材を積層した電極が記載されており（請求項１）、電極活物質の粒子の表面に炭素材料が付着した電極材料が記載されているが（請求項２）、電極合材の粉体抵抗率や剥離強度は考慮されていない。 In an example of Patent Document 3, 100 parts by mass of a positive electrode active material containing lithium ions, 5 parts by mass of a conductive aid, 5 parts by mass of a binder, and 1 part by mass of a thickener are placed on a current collector. A positive electrode provided with a positive electrode active material layer consisting of is described. It is shown that the examples in which the surface of the positive electrode active material is coated with carbon have improved cycle characteristics compared to the comparative example in which the surface is not coated with carbon.
In Patent Document 4, a coating layer containing conductive particles and a binder is provided on the surface of a metal foil, and an electrode mixture containing an electrode active material and 0 to 1.4% by mass of a conductive aid is provided thereon. Laminated electrodes are described (claim 1), and an electrode material in which a carbon material is attached to the surface of the electrode active material particles (claim 2) is described, but the powder resistivity of the electrode mixture and Peel strength is not considered.

国際公開第２０１７／２０８８９４号WO2017/208894 国際公開第２０１８／１６８０５９号WO2018/168059 特開２０１４－１７１９９号公報JP 2014-17199 A 国際公開第２０１３／００５７３９号WO2013/005739

非水電解質二次電池の用途拡大の観点から、高温環境下でも電池特性を良好に維持できる耐熱性が求められる。
そこで、本発明は、非水電解質二次電池の耐熱性を向上できる非水電解質二次電池用正極を提供することを目的とする。 From the viewpoint of expanding the use of non-aqueous electrolyte secondary batteries, there is a demand for heat resistance that can maintain good battery characteristics even in high-temperature environments.
Accordingly, an object of the present invention is to provide a positive electrode for a non-aqueous electrolyte secondary battery that can improve the heat resistance of the non-aqueous electrolyte secondary battery.

また、従来の方法により得られる非水電解質二次電池は、急速充放電サイクル特性等の電池特性の観点から必ずしも充分なものではなかった。
そこで、本発明は、非水電解質二次電池の急速充放電サイクル特性を向上できる非水電解質二次電池用正極を提供することを目的とする。 In addition, non-aqueous electrolyte secondary batteries obtained by conventional methods are not necessarily satisfactory from the viewpoint of battery characteristics such as rapid charge-discharge cycle characteristics.
Accordingly, an object of the present invention is to provide a positive electrode for a non-aqueous electrolyte secondary battery that can improve the rapid charge/discharge cycle characteristics of the non-aqueous electrolyte secondary battery.

しかし、特許文献３、４に記載の方法についても必ずしも充分ではなく、電池特性のさらなる向上が求められている。
そこで、本発明は、正極活物質層の剥離強度が良好であり、非水電解質二次電池のインピーダンスを低減できる非水電解質二次電池用正極を提供することを目的とする。 However, the methods described in Patent Documents 3 and 4 are not necessarily satisfactory, and further improvement in battery characteristics is desired.
Accordingly, an object of the present invention is to provide a positive electrode for a non-aqueous electrolyte secondary battery in which the positive electrode active material layer has good peel strength and the impedance of the non-aqueous electrolyte secondary battery can be reduced.

本発明は以下の態様を有する。
［Ａ１］ 集電体と、前記集電体上に存在する、正極活物質粒子を含む正極活物質層を有し、前記正極活物質層の拡がり抵抗値分布において、抵抗値４．０～１２．５（ｌｏｇΩ）の頻度合計を１００％とするとき、抵抗値４．０～６．０（ｌｏｇΩ）の頻度合計が０．０～５．０％であり、好ましくは０．０～４．０％であり、より好ましくは０．０～３．０％であり、さらに好ましくは０．０～２．０％である、非水電解質二次電池用正極。［Ａ２］ 前記拡がり抵抗値分布において、抵抗値４．０～６．０（ｌｏｇΩ）の平均頻度（平均頻度Ａ、％）より、抵抗値６．０～９．０（ｌｏｇΩ）の平均頻度（平均頻度Ｂ、％）が大きく（即ち、Ａ＜Ｂ）、平均頻度Ａと平均頻度Ｂとの差（Ｂ－Ａ）は０％超が好ましく、０．０５％以上がより好ましく、０．２０％以上がさらに好ましい、［Ａ１］の非水電解質二次電池用正極。
［Ａ３］ 前記正極活物質層が導電助剤を含み、前記導電助剤は、グラファイト、グラフェン、ハードカーボン、ケッチェンブラック、アセチレンブラック、及びカーボンナノチューブ（ＣＮＴ）からなる群より選ばれる少なくとも１種の炭素材料であることが好ましく、正極活物質層における導電助剤の含有量は、正極活物質の総質量１００質量部に対して、４質量部以下が好ましく、３質量部以下がより好ましく、１質量部以下がさらに好ましい、［Ａ１］又は［Ａ２］の非水電解質二次電池用正極。
［Ａ４］ 前記正極活物質粒子の表面の少なくとも一部に、導電材料を含む活物質被覆部が存在する、［Ａ３］の非水電解質二次電池用正極。
［Ａ５］ 前記正極活物質層が導電助剤を含まず、前記正極活物質粒子の表面の少なくとも一部に、導電材料を含む活物質被覆部が存在する、［Ａ１］又は［Ａ２］の非水電解質二次電池用正極。
［Ａ６］ 前記正極活物質層が導電性炭素を含み、前記正極活物質層の総質量に対して前記導電性炭素の含有量が０．５質量％以上３．０質量％未満であり、１．０～２．８質量％がより好ましく、１．３～２．５質量％がさらに好ましい、［Ａ３］～［Ａ５］のいずれかの非水電解質二次電池用正極。
［Ａ７］ 前記正極活物質粒子が、一般式ＬｉＦｅｘＭ（１－ｘ）ＰＯ４（式中、０≦ｘ≦１、ＭはＣｏ、Ｎｉ、Ｍｎ、Ａｌ、Ｔｉ又はＺｒである。）で表される化合物を含み、前記化合物はＬｉＦｅＰＯ４で表されるリン酸鉄リチウムであることが好ましい、［Ａ１］～［Ａ６］のいずれかの非水電解質二次電池用正極。
［Ａ８］ 前記集電体の、前記正極活物質層側の表面の少なくとも一部に、導電材料を含む集電体被覆層が存在し、前記表面において集電体被覆層が存在する部分の面積が、前記表面の総面積に対して、好ましくは１０％～１００％、より好ましくは３０％～１００％、さらに好ましくは５０％～１００％である、［Ａ１］～［Ａ７］のいずれかの非水電解質二次電池用正極。
［Ａ９］ ［Ａ１］～［Ａ８］のいずれかの非水電解質二次電池用正極、負極、及び前記非水電解質二次電池用正極と負極との間に存在する非水電解質を備える、非水電解質二次電池。
［Ａ１０］ ［Ａ９］に記載の非水電解質二次電池の複数個を備える、電池モジュール又は電池システム。
［Ｂ１］集電体と、前記集電体上に存在する正極活物質層を有し、前記正極活物質層が正極活物質及び導電性炭素材料を含み、前記正極活物質層の総質量に対して、抵抗率が０．１０Ω・ｃｍ以下である低抵抗導電性炭素材料の含有量が０．５質量％以下であり、好ましくは０．３質量％以下であり、より好ましくは０．２質量％以下であり、さらに好ましくは０．１質量％以下である、非水電解質二次電池用正極。
［Ｂ２］ 前記正極活物質層の総質量に対して、抵抗率が０．０２Ω・ｃｍ以下である低抵抗導電性炭素材料の含有量が０．５質量％以下であり、より好ましくは０．３質量％以下であり、さらに好ましくは０．２質量％以下であり、特に好ましくは０．１質量％以下である、［Ｂ１］の非水電解質二次電池用正極。
［Ｂ３］ 前記正極活物質層が、前記正極活物質からなる粒子本体と、前記粒子本体の表面の少なくとも一部に存在する活物質被覆部を含み、前記導電性炭素材料の少なくとも一部が前記活物質被覆部であり、前記活物質被覆部の抵抗率が０．１５Ω・ｃｍ以上であり、０．１５Ω・ｃｍ～１．０Ω・ｃｍであることが好ましく、０．２０Ω・ｃｍ～０．５Ω・ｃｍであることがより好ましく、０．２５Ω・ｃｍ～０．４Ω・ｃｍであることがさらに好ましい、［Ｂ１］又は［Ｂ２］の非水電解質二次電池用正極。
［Ｂ４］前記正極活物質層の総質量に対して、前記活物質被覆部の含有量が０．９質量％以上であり、１．０質量％以上であることが好ましく、１．１質量％以上であることがより好ましい、［Ｂ３］の非水電解質二次電池用正極。
［Ｂ５］ 前記正極活物質層が導電助剤を含み、前記導電性炭素材料の少なくとも一部が前記導電助剤であって、前記導電助剤は、グラファイト、グラフェン、ハードカーボン、ケッチェンブラック、アセチレンブラック、及びカーボンナノチューブ（ＣＮＴ）からなる群より選ばれる少なくとも１種の炭素材料であることが好ましく、正極活物質層における導電助剤の含有量は、正極活物質層の総質量に対して、４質量％以下が好ましく、３質量％以下がより好ましく、１質量％以下がさらに好ましい、［Ｂ１］～［Ｂ４］のいずれかの非水電解質二次電池用正極。
［Ｂ６］ 前記正極活物質が、一般式ＬｉＦｅｘＭ（１－ｘ）ＰＯ４（式中、０≦ｘ≦１、ＭはＣｏ、Ｎｉ、Ｍｎ、Ａｌ、Ｔｉ又はＺｒである。）で表される化合物を含み、前記化合物はＬｉＦｅＰＯ４で表されるリン酸鉄リチウムであることが好ましい、［Ｂ１］～［Ｂ５］のいずれかの非水電解質二次電池用正極。
［Ｂ７］ 前記［Ｂ１］～［Ｂ６］のいずれかの非水電解質二次電池用正極、負極、及び前記非水電解質二次電池用正極と負極との間に存在する非水電解質を備える、非水電解質二次電池。
［Ｂ８］ 前記［Ｂ７］の非水電解質二次電池の複数個を備える、電池モジュール又は電池システム。
［Ｃ１］ 正極集電体と、前記正極集電体上に存在する正極活物質層とを有し、前記正極活物質層が正極活物質を含み、前記正極活物質の表面の少なくとも一部に、導電材料を含む活物質被覆部が存在し、前記正極活物質層の粉体抵抗率が１０～１，０００Ω・ｃｍであり、１５～１００Ω・ｃｍであることが好ましく、２０～５０Ω・ｃｍであることがより好ましい、非水電解質二次電池用正極。
［Ｃ２］ 前記正極活物質層が結着材を含み、前記正極活物質層の総質量に対して、結着材の含有量が０．１～１．０質量％であり、０．３～０．８質量％であることが好ましい、［Ｃ１］の非水電解質二次電池用正極。
［Ｃ３］ 前記結着材がポリフッ化ビニリデンを含む、［Ｃ２］の非水電解質二次電池用正極。
［Ｃ４］ 前記正極活物質層の剥離強度が１０～１，０００ｍＮ／ｃｍであり、２０～５００ｍＮ／ｃｍであることが好ましく、５０～３００ｍＮ／ｃｍであることがさらに好ましい、［Ｃ１］～［Ｃ３］のいずれかの非水電解質二次電池用正極。
［Ｃ５］ 前記正極集電体の両面に前記正極活物質層が存在し、前記両面の正極活物質層の合計の単位面積あたりの質量が２０～１００ｍｇ／ｃｍ２であり、３０～５０ｍｇ／ｃｍ２であることがより好ましい、［Ｃ１］～［Ｃ４］のいずれかの非水電解質二次電池用正極。
［Ｃ６］ 前記正極集電体の、前記正極活物質層側の表面に集電体被覆層が存在する、［Ｃ１］～［Ｃ５］のいずれかの非水電解質二次電池用正極。
［Ｃ７］ 前記集電体被覆層が炭素を含み、炭素粒子（カーボンブラック等）と結着材を含むことが好ましい、［Ｃ６］の非水電解質二次電池用正極。
［Ｃ８］ 前記導電材料が炭素を含み、炭素のみからなることが好ましく、活物質被覆部を有する正極活物質の総質量に対して、前記導電材料の含有量は０．１～３．０質量％が好ましく、０．５～１．５質量％がより好ましく、０．７～１．３質量％がさらに好ましい、［Ｃ１］～［Ｃ７］のいずれかの非水電解質二次電池用正極。
［Ｃ９］ 前記正極活物質が、一般式ＬｉＦｅｘＭ（１－ｘ）ＰＯ４（式中、０≦ｘ≦１、ＭはＣｏ、Ｎｉ、Ｍｎ、Ａｌ、Ｔｉ又はＺｒである。）で表される化合物を含む、［Ｃ１］～［Ｃ８］のいずれかの非水電解質二次電池用正極。
［Ｃ１０］ 前記正極活物質が、ＬｉＦｅＰＯ４で表されるリン酸鉄リチウムである、［Ｃ９］の非水電解質二次電池用正極。
［Ｃ１１］ 前記正極活物質層が、さらに導電助剤を含む、［Ｃ１］～［Ｃ１０］のいずれかの非水電解質二次電池用正極。
［Ｃ１２］ 前記導電助剤が炭素を含み、グラファイト、グラフェン、ハードカーボン、ケッチェンブラック、アセチレンブラック、及びカーボンナノチューブ（ＣＮＴ）からなる群より選ばれる少なくとも１種の炭素材料であることが好ましく、正極活物質層における導電助剤の含有量は、正極活物質の総質量１００質量部に対して、４質量部以下が好ましく、３質量部以下がより好ましく、１質量部以下がさらに好ましい、［Ｃ１１］の非水電解質二次電池用正極。
［Ｃ１３］ 前記正極活物質層が導電助剤を含まない、［Ｃ１］～［Ｃ１０］のいずれかの非水電解質二次電池用正極。
［Ｃ１４］ 前記［Ｃ１］～［Ｃ１３］のいずれかの非水電解質二次電池用正極、負極、及び前記非水電解質二次電池用正極と負極との間に存在する非水電解質を備える、非水電解質二次電池。
［Ｃ１５］ 重量エネルギー密度が１２０Ｗｈ／ｋｇ以上であり、好ましくは１３０Ｗｈ／ｋｇ以上であり、より好ましくは１４０Ｗｈ／ｋｇ以上である、［Ｃ１４］の非水電解質二次電池。
［Ｃ１６］ ［Ｃ１４］又は［Ｃ１５］の非水電解質二次電池の複数個を備える、電池モジュール又は電池システム。 The present invention has the following aspects.
[A1] A current collector and a positive electrode active material layer containing positive electrode active material particles present on the current collector, wherein the spreading resistance value distribution of the positive electrode active material layer has a resistance value of 4.0 to 12. When the total frequency of resistance values of 4.0 to 6.0 (log Ω) is 0.0 to 5.0%, preferably 0.0 to 4.0%, when the total frequency of resistance values of 4.0 to 6.0 (log Ω) is 100%. A positive electrode for a non-aqueous electrolyte secondary battery, which is 0%, more preferably 0.0 to 3.0%, and still more preferably 0.0 to 2.0%. [A2] In the spreading resistance value distribution, the average frequency of resistance values 6.0 to 9.0 (log Ω) ( The average frequency B, %) is large (that is, A < B), and the difference (BA) between the average frequency A and the average frequency B is preferably more than 0%, more preferably 0.05% or more, and 0.20 % or more, the positive electrode for a non-aqueous electrolyte secondary battery of [A1].
[A3] The positive electrode active material layer contains a conductive aid, and the conductive aid is at least one selected from the group consisting of graphite, graphene, hard carbon, ketjen black, acetylene black, and carbon nanotubes (CNT). The content of the conductive aid in the positive electrode active material layer is preferably 4 parts by mass or less, more preferably 3 parts by mass or less, with respect to 100 parts by mass of the total mass of the positive electrode active material, The positive electrode for a non-aqueous electrolyte secondary battery of [A1] or [A2], which is more preferably 1 part by mass or less.
[A4] The positive electrode for a non-aqueous electrolyte secondary battery according to [A3], wherein an active material coating containing a conductive material is present on at least part of the surface of the positive electrode active material particles.
[A5] The non-active material of [A1] or [A2], wherein the positive electrode active material layer does not contain a conductive aid, and an active material coating portion containing a conductive material is present on at least part of the surface of the positive electrode active material particles. Positive electrode for water electrolyte secondary battery.
[A6] the positive electrode active material layer contains conductive carbon, and the content of the conductive carbon is 0.5% by mass or more and less than 3.0% by mass with respect to the total mass of the positive electrode active material layer; The positive electrode for a non-aqueous electrolyte secondary battery according to any one of [A3] to [A5], which is more preferably 0 to 2.8% by mass, further preferably 1.3 to 2.5% by mass.
[A7] The positive electrode active material particles have the general formula LiFe x M (1-x) PO 4 (where 0≦x≦1 and M is Co, Ni, Mn, Al, Ti or Zr). The positive electrode for a non-aqueous electrolyte secondary battery according to any one of [A1] to [A6], wherein the compound is preferably lithium iron phosphate represented by LiFePO 4 .
[A8] A current collector coating layer containing a conductive material is present on at least part of the surface of the current collector on the positive electrode active material layer side, and the area of the portion of the surface where the current collector coating layer is present is preferably 10% to 100%, more preferably 30% to 100%, and even more preferably 50% to 100% of the total area of the surface, any one of [A1] to [A7] Positive electrode for non-aqueous electrolyte secondary batteries.
[A9] A nonaqueous electrolyte comprising a positive electrode and a negative electrode for a nonaqueous electrolyte secondary battery according to any one of [A1] to [A8], and a nonaqueous electrolyte present between the positive electrode and the negative electrode for a nonaqueous electrolyte secondary battery. Water electrolyte secondary battery.
[A10] A battery module or battery system comprising a plurality of non-aqueous electrolyte secondary batteries according to [A9].
[B1] has a current collector and a positive electrode active material layer present on the current collector, the positive electrode active material layer contains a positive electrode active material and a conductive carbon material, and the total mass of the positive electrode active material layer In contrast, the content of the low-resistance conductive carbon material having a resistivity of 0.10 Ω·cm or less is 0.5% by mass or less, preferably 0.3% by mass or less, and more preferably 0.2% by mass. A positive electrode for a non-aqueous electrolyte secondary battery having a content of 0.1% by mass or less, preferably 0.1% by mass or less.
[B2] The content of the low-resistance conductive carbon material having a resistivity of 0.02 Ω·cm or less is 0.5% by mass or less, more preferably 0.5% by mass or less, relative to the total mass of the positive electrode active material layer. The positive electrode for a non-aqueous electrolyte secondary battery of [B1], which is 3% by mass or less, more preferably 0.2% by mass or less, and particularly preferably 0.1% by mass or less.
[B3] The positive electrode active material layer includes a particle body made of the positive electrode active material and an active material coating portion present on at least part of the surface of the particle body, and at least part of the conductive carbon material is the The active material coating portion has a resistivity of 0.15 Ω·cm or more, preferably 0.15 Ω·cm to 1.0 Ω·cm, and 0.20 Ω·cm to 0.20 Ω·cm. The positive electrode for a non-aqueous electrolyte secondary battery of [B1] or [B2], which is more preferably 5 Ω·cm, further preferably 0.25 Ω·cm to 0.4 Ω·cm.
[B4] The content of the active material coating portion is 0.9% by mass or more, preferably 1.0% by mass or more, and 1.1% by mass with respect to the total mass of the positive electrode active material layer. The positive electrode for a non-aqueous electrolyte secondary battery of [B3], which is more preferably the above.
[B5] The positive electrode active material layer contains a conductive aid, and at least part of the conductive carbon material is the conductive aid, and the conductive aid is graphite, graphene, hard carbon, ketjen black, It is preferably at least one carbon material selected from the group consisting of acetylene black and carbon nanotubes (CNT), and the content of the conductive aid in the positive electrode active material layer is relative to the total mass of the positive electrode active material layer. , preferably 4% by mass or less, more preferably 3% by mass or less, and further preferably 1% by mass or less, the positive electrode for a non-aqueous electrolyte secondary battery according to any one of [B1] to [B4].
[B6] The positive electrode active material is represented by the general formula LiFe x M (1-x) PO 4 (where 0≦x≦1 and M is Co, Ni, Mn, Al, Ti or Zr). and the compound is preferably lithium iron phosphate represented by LiFePO 4 .
[B7] A positive electrode for a non-aqueous electrolyte secondary battery according to any one of [B1] to [B6], a negative electrode, and a non-aqueous electrolyte present between the positive electrode and the negative electrode for a non-aqueous electrolyte secondary battery, Non-aqueous electrolyte secondary battery.
[B8] A battery module or battery system comprising a plurality of non-aqueous electrolyte secondary batteries of [B7].
[C1] A positive electrode current collector, and a positive electrode active material layer present on the positive electrode current collector, wherein the positive electrode active material layer contains a positive electrode active material, and at least part of the surface of the positive electrode active material , there is an active material coating portion containing a conductive material, and the powder resistivity of the positive electrode active material layer is 10 to 1,000 Ω cm, preferably 15 to 100 Ω cm, and preferably 20 to 50 Ω cm A positive electrode for a non-aqueous electrolyte secondary battery, which is more preferably:
[C2] The positive electrode active material layer contains a binder, and the content of the binder is 0.1 to 1.0% by mass, and 0.3 to 0.3% by mass with respect to the total mass of the positive electrode active material layer. The positive electrode for a non-aqueous electrolyte secondary battery of [C1], which is preferably 0.8% by mass.
[C3] The positive electrode for a non-aqueous electrolyte secondary battery of [C2], wherein the binder contains polyvinylidene fluoride.
[C4] The positive electrode active material layer has a peel strength of 10 to 1,000 mN/cm, preferably 20 to 500 mN/cm, more preferably 50 to 300 mN/cm, [C1] to [ C3] for a positive electrode for a non-aqueous electrolyte secondary battery.
[C5] The positive electrode active material layers are present on both sides of the positive electrode current collector, and the total mass per unit area of the positive electrode active material layers on both sides is 20 to 100 mg/cm 2 and 30 to 50 mg/cm. 2 , the positive electrode for a non-aqueous electrolyte secondary battery according to any one of [C1] to [C4].
[C6] The positive electrode for a non-aqueous electrolyte secondary battery according to any one of [C1] to [C5], wherein a current collector coating layer is present on the surface of the positive electrode current collector on the positive electrode active material layer side.
[C7] The positive electrode for a non-aqueous electrolyte secondary battery of [C6], wherein the current collector coating layer contains carbon, and preferably contains carbon particles (such as carbon black) and a binder.
[C8] It is preferable that the conductive material contains carbon and consists only of carbon, and the content of the conductive material is 0.1 to 3.0 mass relative to the total mass of the positive electrode active material having the active material coating. %, more preferably 0.5 to 1.5% by mass, and even more preferably 0.7 to 1.3% by mass, the positive electrode for a non-aqueous electrolyte secondary battery according to any one of [C1] to [C7].
[C9] The positive electrode active material is represented by the general formula LiFe x M (1-x) PO 4 (where 0≦x≦1 and M is Co, Ni, Mn, Al, Ti or Zr). A positive electrode for a non-aqueous electrolyte secondary battery according to any one of [C1] to [C8], which contains a compound of
[C10] The positive electrode for a nonaqueous electrolyte secondary battery of [C9], wherein the positive electrode active material is lithium iron phosphate represented by LiFePO4 .
[C11] The positive electrode for a non-aqueous electrolyte secondary battery according to any one of [C1] to [C10], wherein the positive electrode active material layer further contains a conductive aid.
[C12] The conductive agent contains carbon and is preferably at least one carbon material selected from the group consisting of graphite, graphene, hard carbon, ketjen black, acetylene black, and carbon nanotubes (CNT), [ C11] positive electrode for a non-aqueous electrolyte secondary battery.
[C13] The positive electrode for a nonaqueous electrolyte secondary battery according to any one of [C1] to [C10], wherein the positive electrode active material layer does not contain a conductive aid.
[C14] A positive electrode for a non-aqueous electrolyte secondary battery according to any one of [C1] to [C13], a negative electrode, and a non-aqueous electrolyte present between the positive electrode and the negative electrode for a non-aqueous electrolyte secondary battery, Non-aqueous electrolyte secondary battery.
[C15] The non-aqueous electrolyte secondary battery of [C14], which has a weight energy density of 120 Wh/kg or more, preferably 130 Wh/kg or more, and more preferably 140 Wh/kg or more.
[C16] A battery module or battery system comprising a plurality of non-aqueous electrolyte secondary batteries of [C14] or [C15].

本発明によれば、非水電解質二次電池の耐熱性を向上できる非水電解質二次電池用正極が得られる。
また、本発明によれば、非水電解質二次電池の急速充放電サイクル特性を向上できる非水電解質二次電池用正極が得られる。
さらに、本発明によれば、正極活物質層の剥離強度が良好であり、非水電解質二次電池のインピーダンスを低減できる非水電解質二次電池用正極が得られる。 ADVANTAGE OF THE INVENTION According to this invention, the positive electrode for nonaqueous electrolyte secondary batteries which can improve the heat resistance of a nonaqueous electrolyte secondary battery is obtained.
Moreover, according to the present invention, a positive electrode for a non-aqueous electrolyte secondary battery can be obtained that can improve the rapid charge/discharge cycle characteristics of the non-aqueous electrolyte secondary battery.
Furthermore, according to the present invention, it is possible to obtain a positive electrode for a non-aqueous electrolyte secondary battery in which the positive electrode active material layer has good peel strength and the impedance of the non-aqueous electrolyte secondary battery can be reduced.

本発明に係る非水電解質二次電池用正極の一例を模式的に示す断面図である。1 is a cross-sectional view schematically showing an example of a positive electrode for a non-aqueous electrolyte secondary battery according to the present invention; FIG. 本発明に係る非水電解質二次電池の一例を模式的に示す断面図である。1 is a cross-sectional view schematically showing an example of a non-aqueous electrolyte secondary battery according to the present invention; FIG. 拡がり抵抗値分布の測定結果を示すマッピング画像である。It is a mapping image showing the measurement results of the spreading resistance value distribution. 拡がり抵抗値分布の測定結果を示すマッピング画像である。It is a mapping image showing the measurement results of the spreading resistance value distribution. 拡がり抵抗値分布の測定結果を示すグラフである。7 is a graph showing measurement results of spreading resistance value distribution. 正極活物質層の剥離強度の測定方法を説明するための工程図である。It is process drawing for demonstrating the measuring method of the peeling strength of a positive electrode active material layer.

本明細書及び特許請求の範囲において、数値範囲を示す「～」は、その前後に記載した数値を下限値及び上限値として含むことを意味する。
図１は、本発明の非水電解質二次電池用正極の一実施形態を示す模式断面図であり、図２は本発明の非水電解質二次電池の一実施形態を示す模式断面図である。
なお、図１、２は、その構成をわかりやすく説明するための模式図であり、各構成要素の寸法比率等は、実際とは異なる場合もある。 In the present specification and claims, "-" indicating a numerical range means that the numerical values before and after it are included as lower and upper limits.
FIG. 1 is a schematic cross-sectional view showing one embodiment of a positive electrode for a non-aqueous electrolyte secondary battery of the present invention, and FIG. 2 is a schematic cross-sectional view showing one embodiment of a non-aqueous electrolyte secondary battery of the present invention. .
1 and 2 are schematic diagrams for explaining the configuration in an easy-to-understand manner, and the dimensional ratios and the like of each component may differ from the actual ones.

＜非水電解質二次電池用正極＞
本実施形態の非水電解質二次電池用正極（単に「正極」ともいう。）１は、集電体（以下「正極集電体」という。）１１と正極活物質層１２を有する。
正極活物質層１２は正極集電体１１の少なくとも一面上に存在する。正極集電体１１の両面上に正極活物質層１２が存在してもよい。
図１の例において、正極集電体１１は、正極活物質層１２側の表面に集電体被覆層１５が存在する。すなわち、正極集電体１１は、正極集電体本体１４と、正極集電体本体１４の正極活物質層１２側の表面を被覆する集電体被覆層１５とを有する。正極集電体本体１４のみを正極集電体１１としてもよい。 <Positive electrode for non-aqueous electrolyte secondary battery>
A positive electrode for a non-aqueous electrolyte secondary battery (also simply referred to as “positive electrode”) 1 of this embodiment has a current collector (hereinafter referred to as “positive electrode current collector”) 11 and a positive electrode active material layer 12 .
The positive electrode active material layer 12 exists on at least one surface of the positive electrode current collector 11 . A positive electrode active material layer 12 may be present on both surfaces of the positive electrode current collector 11 .
In the example of FIG. 1, the positive electrode current collector 11 has a current collector coating layer 15 on the surface of the positive electrode active material layer 12 side. That is, the positive electrode current collector 11 has a positive electrode current collector main body 14 and a current collector coating layer 15 that covers the surface of the positive electrode current collector main body 14 on the positive electrode active material layer 12 side. Only the positive electrode current collector main body 14 may be used as the positive electrode current collector 11 .

－ 第１の実施形態 －
本発明の第１の実施形態に係る非水電解質二次電池用正極１は、集電体１１と、前記集電体１１上に存在する、正極活物質粒子を含む正極活物質層１２を有し、前記正極活物質層１２の拡がり抵抗値分布において、抵抗値４．０～１２．５（ｌｏｇΩ）の頻度合計を１００％とするとき、抵抗値４．０～６．０（ｌｏｇΩ）の頻度合計が０．０～５．０％である。
上記構成を有する非水電解質二次電池用正極１は、非水電解質二次電池の耐熱性を向上できる。
以下に具体的に説明する。 - 1st embodiment -
A positive electrode 1 for a non-aqueous electrolyte secondary battery according to the first embodiment of the present invention has a current collector 11 and a positive electrode active material layer 12 containing positive electrode active material particles present on the current collector 11. Then, in the spreading resistance value distribution of the positive electrode active material layer 12, when the total frequency of the resistance values 4.0 to 12.5 (log Ω) is 100%, the resistance values 4.0 to 6.0 (log Ω) The total frequency is 0.0-5.0%.
The positive electrode 1 for a non-aqueous electrolyte secondary battery having the above structure can improve the heat resistance of the non-aqueous electrolyte secondary battery.
A specific description will be given below.

［正極活物質層］
正極活物質層１２は正極活物質粒子を含む。
正極活物質層１２は、さらに結着材を含むことが好ましい。
正極活物質層１２は、さらに導電助剤を含んでもよい。本明細書において、「導電助剤」という用語は、正極活物質層を形成するにあたって正極活物質粒子と混合する、粒状、繊維状などの形状を有する導電材料であって、正極活物質粒子を繋ぐ形で正極活物質層中に存在させる導電材料を指す。
正極活物質層１２は、さらに分散剤を含んでもよい。
正極活物質層１２の総質量に対して、正極活物質粒子の含有量は８０．０～９９．９質量％が好ましく、９０～９９．５質量％がより好ましい。 [Positive electrode active material layer]
The positive electrode active material layer 12 contains positive electrode active material particles.
Preferably, the positive electrode active material layer 12 further contains a binder.
The positive electrode active material layer 12 may further contain a conductive aid. As used herein, the term “conductive aid” refers to a conductive material having a shape such as a granular or fibrous shape, which is mixed with the positive electrode active material particles in forming the positive electrode active material layer. It refers to a conductive material present in the positive electrode active material layer in a form of connection.
The positive electrode active material layer 12 may further contain a dispersant.
The content of the positive electrode active material particles is preferably 80.0 to 99.9% by mass, more preferably 90 to 99.5% by mass, based on the total mass of the positive electrode active material layer 12 .

正極活物質層の厚み（正極集電体の両面上に正極活物質層が存在する場合、両面の合計）は３０～５００μｍであることが好ましく、４０～４００μｍであることがより好ましく、５０～３００μｍであることが特に好ましい。正極活物質層の厚みが上記範囲の下限値以上であると、正極を組み込んだ電池のエネルギー密度が高くなりやすく、上記範囲の上限値以下であると、正極活物質層の剥離強度が高く、充放電時に剥がれを抑制できる。 The thickness of the positive electrode active material layer (when the positive electrode active material layer is present on both sides of the positive electrode current collector, the total thickness of both surfaces) is preferably 30 to 500 μm, more preferably 40 to 400 μm, and 50 to 500 μm. 300 μm is particularly preferred. When the thickness of the positive electrode active material layer is at least the lower limit of the above range, the energy density of the battery incorporating the positive electrode tends to be high. Peeling can be suppressed during charging and discharging.

［正極活物質粒子］
正極活物質粒子の表面の少なくとも一部に、導電材料を含む活物質被覆部が存在することが好ましい（活物質被覆部を有する正極活物質粒子を、以下、「被覆粒子」と称することもある）。電池容量、サイクル特性により優れる点から、正極活物質粒子の表面全体が導電材料で被覆されていることがより好ましい。
ここで、「正極活物質粒子の表面の少なくとも一部」とは、活物質被覆部が、正極活物質粒子の外表面全体の面積の５０％以上、好ましくは７０％以上、より好ましくは９０％以上、特に好ましくは１００％を覆っていることを意味する。なお、この割合（％）（以下、「被覆率」と称することもある。）は、正極活物質層中に存在する正極活物質粒子全体についての平均値であり、この平均値が上記下限値以上となる限り、活物質被覆部を有しない正極活物質粒子が微量に存在することを排除するものではない。活物質被覆部を有しない正極活物質粒子が正極活物質層中に存在する場合、その量は、正極活物質層中に存在する正極活物質粒子全体の量に対して、好ましくは３０質量％以下であり、より好ましくは２０質量％以下であり、特に好ましくは１０質量％以下である。
前記被覆率は次の様な方法により測定することができる。まず、正極活物質層中の粒子を、透過電子顕微鏡を用いたエネルギー分散型Ｘ線分光法（ＴＥＭ－ＥＤＸ）により分析する。具体的には、ＴＥＭ画像における正極活物質粒子の外周部をＥＤＸで元素分析する。元素分析は炭素について行い、正極活物質粒子を被覆している炭素を特定する。炭素による被覆が１ｎｍ以上の厚さである箇所を被覆部分とし、観察した正極活物質粒子の全周に対して被覆部分の割合を求め、これを被覆率とすることができる。測定は例えば、１０個の正極活物質粒子について行い、これらの平均値とすることができる。
また、前記活物質被覆部は、正極活物質のみから構成される粒子（以下、「芯部」と称することもある。）の表面上に直接形成された厚み１ｎｍ～１００ｎｍ、好ましくは５ｎｍ～５０ｎｍの層であり、この厚みは上述した被覆率の測定に用いるＴＥＭ－ＥＤＸによって確認することができる。 [Positive electrode active material particles]
It is preferable that an active material coating portion containing a conductive material is present on at least a part of the surface of the positive electrode active material particle (a positive electrode active material particle having an active material coating portion may be hereinafter referred to as a “coated particle”. ). From the viewpoint of better battery capacity and cycle characteristics, it is more preferable that the entire surface of the positive electrode active material particles is coated with a conductive material.
Here, "at least part of the surface of the positive electrode active material particle" means that the active material coating portion accounts for 50% or more, preferably 70% or more, and more preferably 90% of the total area of the outer surface of the positive electrode active material particle. More preferably, it means 100% coverage. Note that this ratio (%) (hereinafter sometimes referred to as “coverage”) is the average value for the entire positive electrode active material particles present in the positive electrode active material layer, and this average value is the above lower limit. As far as the above is concerned, it is not excluded that a small amount of positive electrode active material particles not having an active material coating portion are present. When the positive electrode active material particles that do not have the active material coating part are present in the positive electrode active material layer, the amount thereof is preferably 30% by mass with respect to the total amount of the positive electrode active material particles present in the positive electrode active material layer. or less, more preferably 20% by mass or less, and particularly preferably 10% by mass or less.
The coverage can be measured by the following method. First, particles in the positive electrode active material layer are analyzed by energy dispersive X-ray spectroscopy (TEM-EDX) using a transmission electron microscope. Specifically, the outer peripheral portion of the positive electrode active material particles in the TEM image is subjected to elemental analysis by EDX. Elemental analysis is performed on carbon to identify the carbon coating the positive electrode active material particles. A portion where the coating with carbon has a thickness of 1 nm or more is defined as a coated portion, and the ratio of the coated portion to the entire circumference of the observed positive electrode active material particle is obtained, and this can be used as the coverage rate. For example, ten positive electrode active material particles are measured, and the average value thereof can be obtained.
In addition, the active material coating part is formed directly on the surface of a particle (hereinafter sometimes referred to as a "core part") composed only of a positive electrode active material and has a thickness of 1 nm to 100 nm, preferably 5 nm to 50 nm. This thickness can be confirmed by TEM-EDX used for the measurement of the coverage rate described above.

活物質被覆部の導電材料は、炭素（導電性炭素）を含むことが好ましい。炭素のみからなる導電材料でもよく、炭素と炭素以外の他の元素とを含む導電性有機化合物でもよい。他の元素としては、窒素、水素、酸素等が例示できる。前記導電性有機化合物において、他の元素は１０原子％以下が好ましく、５原子％以下がより好ましい。
活物質被覆部を構成する導電材料は、炭素のみからなることがさらに好ましい。
活物質被覆部を有する正極活物質粒子の総質量に対して、導電材料の含有量は０．１～４．０質量％が好ましく、０．５～３．０質量％がより好ましく、０．７～２．５質量％がさらに好ましい。多すぎる場合は正極活物質粒子の表面から導電材料が剥がれ、独立した導電助剤粒子として残留する可能性があるため、好ましくない。 The conductive material of the active material coating preferably contains carbon (conductive carbon). A conductive material consisting only of carbon may be used, or a conductive organic compound containing carbon and an element other than carbon may be used. Nitrogen, hydrogen, oxygen and the like can be exemplified as other elements. In the conductive organic compound, the content of other elements is preferably 10 atomic % or less, more preferably 5 atomic % or less.
It is more preferable that the conductive material constituting the active material coating portion is made of carbon only.
The content of the conductive material is preferably 0.1 to 4.0% by mass, more preferably 0.5 to 3.0% by mass, and 0.1 to 4.0% by mass, more preferably 0.5 to 3.0% by mass, based on the total mass of the positive electrode active material particles having the active material coating portion. 7 to 2.5% by mass is more preferable. If the amount is too large, the conductive material may peel off from the surface of the positive electrode active material particles and remain as independent conductive auxiliary particles, which is not preferable.

例えば、活物質被覆部は、予め正極活物質粒子の表面に形成されており、かつ正極活物質層中において、正極活物質粒子の表面に存在する。即ち、本実施形態における活物質被覆部は、正極製造用組成物の調製段階以降の工程で新たに形成されるものではない。加えて、活物質被覆部は、正極製造用組成物の調製段階以降の工程で欠落するものではない。
例えば、正極製造用組成物を調製する際に、被覆粒子を溶媒と共にミキサー等で混合しても、活物質被覆部は正極活物質の表面を被覆している。また、仮に、正極から正極活物質層を剥がし、これを溶媒に投入して正極活物質層中の結着材を溶媒に溶解させた場合にも、活物質被覆部は正極活物質の表面を被覆している。また、仮に、正極活物質層中の粒子の粒度分布をレーザー回折・散乱法により測定する際に、凝集した粒子をほぐす操作を行った場合にも活物質被覆部は正極活物質の表面を被覆している。 For example, the active material coating portion is formed in advance on the surfaces of the positive electrode active material particles, and is present on the surfaces of the positive electrode active material particles in the positive electrode active material layer. That is, the active material coating portion in the present embodiment is not newly formed in the steps after the step of preparing the positive electrode manufacturing composition. In addition, the active material coating portion does not fall off in the steps after the step of preparing the composition for manufacturing a positive electrode.
For example, even when the coated particles are mixed with a solvent in a mixer or the like when preparing the positive electrode-manufacturing composition, the active material-coating portion still covers the surface of the positive electrode active material. Further, even if the positive electrode active material layer is peeled off from the positive electrode and put into a solvent to dissolve the binder in the positive electrode active material layer in the solvent, the active material coating part covers the surface of the positive electrode active material. covered. In addition, even if the particle size distribution of the particles in the positive electrode active material layer is measured by a laser diffraction/scattering method, even if an operation is performed to loosen the aggregated particles, the active material coating portion covers the surface of the positive electrode active material. are doing.

被覆粒子の製造方法としては、例えば、焼結法、蒸着法等が挙げられる。
焼結法としては、正極活物質の粒子と有機物とを含む活物質製造用組成物（例えば、スラリー）を、大気圧下、５００～１０００℃、１～１００時間で焼成する方法が挙げられる。活物質製造用組成物に添加する有機物としては、サリチル酸、カテコール、ヒドロキノン、レゾルシノール、ピロガロール、フロログルシノール、ヘキサヒドロキシベンゼン、安息香酸、フタル酸、テレフタル酸、フェニルアラニン、水分散型フェノール樹脂等、スクロース、グルコース、ラクトース等の糖類、リンゴ酸、クエン酸などのカルボン酸、アリルアルコール、プロパルギルアルコール等の不飽和一価アルコール、アスコルビン酸、ポリビニルアルコール等が挙げられる。この焼結法によれば、活物質製造用組成物を焼成することで、有機物中の炭素を正極活物質の表面に焼結して、活物質被覆部を形成する。
また、他の焼結法としては、いわゆる衝撃焼結被覆法が挙げられる。 Examples of the method for producing coated particles include a sintering method and a vapor deposition method.
Examples of the sintering method include a method in which a composition for producing an active material (eg, slurry) containing positive electrode active material particles and an organic substance is fired at 500 to 1000° C. for 1 to 100 hours under atmospheric pressure. Examples of organic substances added to the active material-producing composition include salicylic acid, catechol, hydroquinone, resorcinol, pyrogallol, phloroglucinol, hexahydroxybenzene, benzoic acid, phthalic acid, terephthalic acid, phenylalanine, water-dispersed phenolic resin, and sucrose. , glucose and lactose, carboxylic acids such as malic acid and citric acid, unsaturated monohydric alcohols such as allyl alcohol and propargyl alcohol, ascorbic acid, and polyvinyl alcohol. According to this sintering method, the carbon in the organic matter is sintered onto the surface of the positive electrode active material by firing the active material-producing composition to form the active material coating portion.
Another sintering method is the so-called impact sinter coating method.

衝撃焼結被覆法は、例えば、衝撃焼結被覆装置において燃料の炭化水素と酸素の混合ガスを用いてバーナに点火し燃焼室で燃焼させてフレームを発生させ、その際、酸素量を燃料に対して完全燃焼の当量以下にしてフレーム温度を下げ、その後方に粉末供給用ノズルを設置し、そのノズルから被覆する有機物と溶媒を用いて溶かしスラリー状にしたものと燃焼ガスからなる固体―液体―気体三相混合物を粉末供給ノズルから噴射させ、室温に保持された燃焼ガス量を増して、噴射微粉末の温度を下げて、粉末材料の変態温度、昇華温度、蒸発温度以下で加速し、衝撃により瞬時焼結させて、正極活物質の粒子を被覆する。 蒸着法としては、物理気相成長法（ＰＶＤ）、化学気相成長法（ＣＶＤ）等の気相堆積法、メッキ等の液相堆積法等が挙げられる。 In the impact sintering coating method, for example, in an impact sintering coating device, a mixed gas of hydrocarbon and oxygen as a fuel is used to ignite a burner and burn it in a combustion chamber to generate a flame. On the other hand, the flame temperature is lowered to below the equivalent of complete combustion, and a powder supply nozzle is installed behind it, and the solid-liquid consisting of the organic matter to be coated and the slurry melted using the solvent and the combustion gas from the nozzle. - Injecting the gaseous three-phase mixture from the powder feed nozzle, increasing the amount of combustion gas maintained at room temperature, lowering the temperature of the injected fine powder, and accelerating it below the transformation temperature, sublimation temperature, and evaporation temperature of the powder material, Instantly sintered by impact to coat the particles of the positive electrode active material. Vapor deposition methods include physical vapor deposition (PVD), chemical vapor deposition (CVD) and other vapor phase deposition methods, and liquid phase deposition methods such as plating.

また、正極活物質層の厚み（正極集電体の両面上に正極活物質層が存在する場合、両面の合計）は３０～５００μｍであることが好ましく、４０～４００μｍであることがより好ましく、５０～３００μｍであることが特に好ましい。正極活物質層の厚みが上記範囲の下限値以上であると、体積当たりのエネルギー密度に優れた電池を製造するための正極を提供でき、上記範囲の上限値以下であると、正極の剥離強度が高く、充放電時に剥がれを抑制できる。 In addition, the thickness of the positive electrode active material layer (when the positive electrode active material layer is present on both sides of the positive electrode current collector, the total thickness of both sides) is preferably 30 to 500 μm, more preferably 40 to 400 μm. Particularly preferred is 50 to 300 μm. When the thickness of the positive electrode active material layer is at least the lower limit value of the above range, it is possible to provide a positive electrode for manufacturing a battery with excellent energy density per volume. is high, and peeling can be suppressed during charging and discharging.

正極活物質粒子は、オリビン型結晶構造を有する化合物を含むことが好ましい。
オリビン型結晶構造を有する化合物は、一般式ＬｉＦｅｘＭ（１－ｘ）ＰＯ４（以下「一般式（Ｉ）」ともいう。）で表される化合物が好ましい。一般式（Ｉ）において０≦ｘ≦１である。ＭはＣｏ、Ｎｉ、Ｍｎ、Ａｌ、Ｔｉ又はＺｒである。物性値に変化がない程度に微小量の、ＦｅおよびＭ（Ｃｏ、Ｎｉ、Ｍｎ、Ａｌ、Ｔｉ又はＺｒ）の一部を他の元素に置換することもできる。一般式（Ｉ）で表される化合物は、微量の金属不純物が含まれていても本発明の効果が損なわれるものではない。 The positive electrode active material particles preferably contain a compound having an olivine crystal structure.
The compound having an olivine-type crystal structure is preferably a compound represented by the general formula LiFe x M (1-x) PO 4 (hereinafter also referred to as "general formula (I)"). 0≦x≦1 in general formula (I). M is Co, Ni, Mn, Al, Ti or Zr. A small amount of Fe and M (Co, Ni, Mn, Al, Ti or Zr) can be substituted with other elements to the extent that the physical properties are not changed. Even if the compound represented by the general formula (I) contains a trace amount of metal impurities, the effect of the present invention is not impaired.

一般式（Ｉ）で表される化合物は、ＬｉＦｅＰＯ４で表されるリン酸鉄リチウム（以下、単に「リン酸鉄リチウム」ともいう。）が好ましい。
正極活物質粒子として、表面の少なくとも一部に導電材料を含む活物質被覆部が存在するリン酸鉄リチウム粒子（以下「被覆リン酸鉄リチウム粒子」ともいう。）がより好ましい。電池容量、サイクル特性により優れる点から、リン酸鉄リチウム粒子の表面全体が導電材料で被覆されていることがさらに好ましい。
被覆リン酸鉄リチウム粒子は公知の方法で製造できる。
例えば、特許第５０９８１４６号公報に記載の方法を用いてリン酸鉄リチウム粉末を作製し、ＧＳ Ｙｕａｓａ Ｔｅｃｈｎｉｃａｌ Ｒｅｐｏｒｔ、２００８年６月、第５巻、第１号、第２７～３１頁等に記載の方法を用いて、リン酸鉄リチウム粉末の表面の少なくとも一部を炭素で被覆できる。
具体的には、まず、シュウ酸鉄二水和物、リン酸二水素アンモニウム、及び炭酸リチウムを、特定のモル比で計り、これらを不活性雰囲気下で粉砕及び混合する。次に、得られた混合物を窒素雰囲気下で加熱処理することによってリン酸鉄リチウム粉末を作製する。次いで、リン酸鉄リチウム粉末をロータリーキルンに入れ、窒素をキャリアガスとしたメタノール蒸気を供給しながら加熱処理することによって、表面の少なくとも一部を炭素で被覆したリン酸鉄リチウム粒子を得る。
例えば、粉砕工程における粉砕時間によってリン酸鉄リチウム粒子の粒子径を調整できる。メタノール蒸気を供給しながら加熱処理する工程における加熱時間及び温度等によって、リン酸鉄リチウム粒子を被覆する炭素の量を調整できる。被覆されなかった炭素粒子はその後の分級や洗浄などの工程などにより取り除くことが望ましい。 The compound represented by the general formula (I) is preferably lithium iron phosphate represented by LiFePO 4 (hereinafter also simply referred to as “lithium iron phosphate”).
As the positive electrode active material particles, lithium iron phosphate particles having active material coating portions containing a conductive material on at least part of their surfaces (hereinafter also referred to as “coated lithium iron phosphate particles”) are more preferable. From the viewpoint of better battery capacity and cycle characteristics, it is more preferable that the lithium iron phosphate particles are entirely coated with a conductive material.
Coated lithium iron phosphate particles can be produced by known methods.
For example, lithium iron phosphate powder is prepared using the method described in Japanese Patent No. 5098146, and described in GS Yuasa Technical Report, June 2008, Vol. 5, No. 1, pp. 27-31. The method can be used to coat at least a portion of the surface of the lithium iron phosphate powder with carbon.
Specifically, first, iron oxalate dihydrate, ammonium dihydrogen phosphate, and lithium carbonate are weighed in a specific molar ratio, and these are pulverized and mixed under an inert atmosphere. Next, a lithium iron phosphate powder is produced by heat-treating the obtained mixture in a nitrogen atmosphere. Next, the lithium iron phosphate powder is placed in a rotary kiln and heat-treated while supplying methanol vapor using nitrogen as a carrier gas to obtain lithium iron phosphate particles having at least a portion of the surface coated with carbon.
For example, the particle size of the lithium iron phosphate particles can be adjusted by the pulverization time in the pulverization step. The amount of carbon covering the lithium iron phosphate particles can be adjusted by the heating time and temperature in the step of heat-treating while supplying methanol vapor. It is desirable to remove uncoated carbon particles by subsequent steps such as classification and washing.

正極活物質粒子は、オリビン型結晶構造を有する化合物以外の他の正極活物質を含む他の正極活物質粒子を１種以上含んでもよい。
他の正極活物質は、リチウム遷移金属複合酸化物が好ましい。例えば、コバルト酸リチウム（ＬｉＣｏＯ２）、ニッケル酸リチウム（ＬｉＮｉＯ２）、ニッケルコバルトアルミン酸リチウム（ＬｉＮｉｘＣｏｙＡｌｚＯ２、ただしｘ＋ｙ＋ｚ＝１）、ニッケルコバルトマンガン酸リチウム（ＬｉＮｉｘＣｏｙＭｎｚＯ２、ただしｘ＋ｙ＋ｚ＝１）、マンガン酸リチウム（ＬｉＭｎ２Ｏ４）、コバルトマンガン酸リチウム（ＬｉＭｎＣｏＯ４）、クロム酸マンガンリチウム（ＬｉＭｎＣｒＯ４）、バナジウムニッケル酸リチウム（ＬｉＮｉＶＯ４）、ニッケル置換マンガン酸リチウム（例えば、ＬｉＭｎ１．５Ｎｉ０．５Ｏ４）、及びバナジウムコバルト酸リチウム（ＬｉＣｏＶＯ４）、これらの化合物の一部を金属元素で置換した非化学量論的化合物等が挙げられる。前記金属元素としては、Ｍｎ、Ｍｇ、Ｎｉ、Ｃｏ、Ｃｕ、Ｚｎ及びＧｅからなる群から選択される１種以上が挙げられる。
他の正極活物質粒子の表面の少なくとも一部に、前記活物質被覆部が存在してもよい。 The positive electrode active material particles may contain at least one other positive electrode active material particle containing a positive electrode active material other than the compound having an olivine crystal structure.
Another positive electrode active material is preferably a lithium transition metal composite oxide. For example, lithium cobalt oxide (LiCoO 2 ), lithium nickel oxide (LiNiO 2 ) , lithium nickel cobalt aluminate ( LiNixCoyAlzO2 , where x + y +z=1), lithium nickel cobalt manganate (LiNixCoyMn zO2 , where x+y+z=1), lithium manganate ( LiMn2O4 ), lithium cobalt manganate ( LiMnCoO4 ), lithium manganese chromate ( LiMnCrO4 ) , lithium vanadium nickelate ( LiNiVO4 ), nickel-substituted manganese Lithium oxide (eg, LiMn 1.5 Ni 0.5 O 4 ), lithium vanadium cobaltate (LiCoVO 4 ), non-stoichiometric compounds obtained by substituting a part of these compounds with metal elements, and the like. Examples of the metal element include one or more selected from the group consisting of Mn, Mg, Ni, Co, Cu, Zn and Ge.
The active material coating portion may be present on at least part of the surface of the other positive electrode active material particles.

正極活物質粒子の総質量（活物質被覆部を有する場合は活物質被覆部の質量も含む）に対して、オリビン型結晶構造を有する化合物の含有量は５０質量％以上が好ましく、８０質量％以上がより好ましく、９０質量％以上がさらに好ましい。１００質量％でもよい。
被覆リン酸鉄リチウム粒子を用いる場合、正極活物質粒子の総質量に対して、被覆リン酸鉄リチウム粒子の含有量は５０質量％以上が好ましく、８０質量％以上がより好ましく、９０質量％以上がさらに好ましい。１００質量％でもよい。 The content of the compound having an olivine-type crystal structure is preferably 50% by mass or more, preferably 80% by mass, based on the total mass of the positive electrode active material particles (including the mass of the active material coating portion when the active material coating portion is included). The above is more preferable, and 90% by mass or more is even more preferable. 100 mass % may be sufficient.
When the coated lithium iron phosphate particles are used, the content of the coated lithium iron phosphate particles is preferably 50% by mass or more, more preferably 80% by mass or more, and 90% by mass or more with respect to the total mass of the positive electrode active material particles. is more preferred. 100 mass % may be sufficient.

正極活物質粒子の活物質被覆部の厚さは、１～１００ｎｍが好ましい。
正極活物質粒子の活物質被覆部の厚さは、正極活物質粒子の透過電子顕微鏡（ＴＥＭ）像における活物質被覆部の厚さを計測する方法で測定できる。正極活物質粒子の表面に存在する活物質被覆部の厚さは均一でなくてもよい。正極活物質粒子の表面の少なくとも一部に厚さ１ｎｍ以上の活物質被覆部が存在し、活物質被覆部の厚さの最大値が１００ｎｍ以下であることが好ましい。 The thickness of the active material coating portion of the positive electrode active material particles is preferably 1 to 100 nm.
The thickness of the active material coating portion of the positive electrode active material particles can be measured by a method of measuring the thickness of the active material coating portion in a transmission electron microscope (TEM) image of the positive electrode active material particles. The thickness of the active material coating portion present on the surface of the positive electrode active material particles may not be uniform. It is preferable that an active material coating portion having a thickness of 1 nm or more exists on at least part of the surface of the positive electrode active material particles, and the maximum thickness of the active material coating portion is 100 nm or less.

正極活物質として用いる粒子（即ち、正極活物質として用いる粉体）の平均粒子径（活物質被覆部を有する場合は活物質被覆部の厚さも含む）は、例えば０．１～２０．０μｍが好ましく、０．２～１０．０μｍがより好ましい。正極活物質を２種以上用いる場合、それぞれの平均粒子径が上記の範囲内であればよい。
本明細書における正極活物質の平均粒子径は、レーザー回折・散乱法による粒度分布測定器を用いて測定した体積基準のメジアン径である。 The average particle diameter of the particles used as the positive electrode active material (that is, the powder used as the positive electrode active material) (including the thickness of the active material coating portion when it has an active material coating portion) is, for example, 0.1 to 20.0 μm. Preferably, 0.2 to 10.0 μm is more preferable. When two or more kinds of positive electrode active materials are used, each average particle size should be within the above range.
The average particle size of the positive electrode active material in the present specification is a volume-based median size measured using a particle size distribution analyzer based on a laser diffraction/scattering method.

［結着材］
正極活物質層１２に含まれる結着材は有機物であり、例えば、ポリアクリル酸、ポリアクリル酸リチウム、ポリフッ化ビニリデン、ポリフッ化ビニリデン－ヘキサフルオロプロピレン共重合体、スチレンブタジエンゴム、ポリビニルアルコール、ポリビニルアセタール、ポリエチレンオキサイド、ポリエチレングリコール、カルボキシメチルセルロース、ポリアクリルニトリル、ポリイミド等が挙げられる。結着材は１種でもよく、２種以上を併用してもよい。
正極活物質層１２が結着剤を含有する場合、正極活物質層１２における結着材の含有量は、例えば、正極活物質層１２の総質量に対して、４．０質量％以下が好ましく、２．０質量％以下がより好ましい。結着材の含有量が上記上限値以下であれば、正極活物質層１２において、リチウムイオンの伝導に寄与しない物質の割合が少なくなり、電池特性のさらなる向上を図れる。
正極活物質層１２が結着材を含有する場合、結着材の含有量の下限値は、正極活物質層１２の総質量に対して０．１質量％以上が好ましく、０．５質量％以上がより好ましい。
即ち、正極活物質層１２が結着材を含有する場合、結着材の含有量は、正極活物質層１２の総質量に対して０．１質量％～４．０質量％が好ましく、０．５質量％～２．０質量％がより好ましい。 [Binder]
The binder contained in the positive electrode active material layer 12 is an organic substance, and examples thereof include polyacrylic acid, lithium polyacrylate, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, styrene-butadiene rubber, polyvinyl alcohol, and polyvinylidene. Acetal, polyethylene oxide, polyethylene glycol, carboxymethyl cellulose, polyacrylonitrile, polyimide and the like can be mentioned. One type of binder may be used, or two or more types may be used in combination.
When the positive electrode active material layer 12 contains a binder, the content of the binder in the positive electrode active material layer 12 is preferably 4.0% by mass or less with respect to the total mass of the positive electrode active material layer 12, for example. , 2.0% by mass or less. If the content of the binder is equal to or less than the above upper limit, the ratio of substances that do not contribute to the conduction of lithium ions in the positive electrode active material layer 12 is reduced, and the battery characteristics can be further improved.
When the positive electrode active material layer 12 contains a binder, the lower limit of the content of the binder is preferably 0.1% by mass or more, more preferably 0.5% by mass, based on the total mass of the positive electrode active material layer 12. The above is more preferable.
That is, when the positive electrode active material layer 12 contains a binder, the content of the binder is preferably 0.1% by mass to 4.0% by mass with respect to the total mass of the positive electrode active material layer 12. 0.5 mass % to 2.0 mass % is more preferred.

［導電助剤］
正極活物質層１２に含まれる導電助剤としては、例えば、ケッチェンブラック、アセチレンブラック等のカーボンブラック、グラファイト、グラフェン、ハードカーボン、カーボンナノチューブ（ＣＮＴ）等の炭素材料が挙げられる。導電助剤は１種でもよく、２種以上を併用してもよい。
正極活物質層における導電助剤の含有量は、例えば、正極活物質の総質量１００質量部に対して、４質量部以下が好ましく、３質量部以下がより好ましく、１質量部以下がさらに好ましく、導電助剤を含まないことが特に好ましく、独立した導電助剤粒子（例えば独立した炭素粒子）が存在しない状態が望ましい。
前記「導電助剤」は、正極活物質とは独立した導電性材料であり、前記独立した導電助剤粒子の他に、繊維状（例えばカーボンナノチューブ）の形状を有する導電性の材料であってもよい。
正極活物質層中において正極活物質粒子に接触している導電助剤は、正極活物質被覆部を構成する導電材料とはみなさない。
正極活物質層に導電助剤を配合する場合、導電助剤の含有量の下限値は、導電助剤の種類に応じて適宜決定され、例えば、正極活物質層の総質量に対して０．１質量％超とされる。
即ち、正極活物質層１２が導電助剤を含有する場合、導電助剤の含有量は、正極活物質の総質量１００質量部に対して、０．２～４質量部が好ましく、０．３～３質量部がより好ましく、０．５～１質量部がさらに好ましい。
なお、正極活物質層が「導電助剤を含まない」とは、実質的に含まないことを意味し、本発明の効果に影響を及ぼさない程度に含むものを排除するものではない。例えば、導電助剤の含有量が正極活物質層の総質量に対して０．１質量％以下であれば、実質的に含まれないと判断できる。
導電助剤として用いる粒子（即ち、導電助剤として用いる粉体）の平均粒子径は、例えば０．００１～１．０μｍが好ましく、０．０１～０．１０μｍがより好ましい。導電助剤を２種以上用いる場合、それぞれの平均粒子径が上記の範囲内であればよい。
本明細書における導電助剤の平均粒子径は、レーザー回折・散乱法による粒度分布測定器を用いて測定した体積基準のメジアン径である。 [Conductive agent]
Examples of the conductive aid contained in the positive electrode active material layer 12 include carbon black such as ketjen black and acetylene black, and carbon materials such as graphite, graphene, hard carbon, and carbon nanotubes (CNT). One type of conductive aid may be used, or two or more types may be used in combination.
The content of the conductive aid in the positive electrode active material layer is, for example, preferably 4 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 1 part by mass or less with respect to 100 parts by mass of the total mass of the positive electrode active material. , it is particularly preferable not to contain a conductive additive, and a state in which independent conductive additive particles (for example, independent carbon particles) do not exist is desirable.
The "conductivity aid" is a conductive material independent of the positive electrode active material, and in addition to the independent conductivity aid particles, is a conductive material having a fibrous (e.g., carbon nanotube) shape. good too.
The conductive aid in contact with the positive electrode active material particles in the positive electrode active material layer is not regarded as a conductive material forming the positive electrode active material coating portion.
When the positive electrode active material layer contains the conductive support agent, the lower limit of the content of the conductive support agent is appropriately determined according to the type of the conductive support agent. More than 1% by mass.
That is, when the positive electrode active material layer 12 contains a conductive agent, the content of the conductive agent is preferably 0.2 to 4 parts by mass, and preferably 0.3 parts by mass, with respect to 100 parts by mass of the total mass of the positive electrode active material. ~3 parts by mass is more preferable, and 0.5 to 1 part by mass is even more preferable.
In addition, the fact that the positive electrode active material layer "does not contain a conductive aid" means that it does not substantially contain a conductive aid, and does not exclude substances contained to such an extent that the effects of the present invention are not affected. For example, if the content of the conductive aid is 0.1% by mass or less with respect to the total mass of the positive electrode active material layer, it can be determined that it is not substantially included.
The average particle size of the particles used as the conductive aid (that is, the powder used as the conductive aid) is, for example, preferably 0.001 to 1.0 μm, more preferably 0.01 to 0.10 μm. When using two or more conductive aids, the average particle size of each should be within the above range.
The average particle size of the conductive additive used herein is a volume-based median size measured using a particle size distribution analyzer based on a laser diffraction/scattering method.

［分散剤］
正極活物質層１２に含まれる分散剤は有機物であり、例えば、ポリビニルピロリドン（ＰＶＰ）、ポリビニルアルコール（ＰＶＡ）、ポリビニルブチラール（ＰＶＢ）、ポリビニルホルマール（ＰＶＦ）等が挙げられる。分散剤は１種でもよく、２種以上を併用してもよい。 [Dispersant]
The dispersant contained in the positive electrode active material layer 12 is an organic substance, and examples thereof include polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinyl formal (PVF), and the like. One dispersant may be used, or two or more dispersants may be used in combination.

［正極集電体本体］
正極集電体本体１４は金属材料からなる。金属材料としては、銅、アルミニウム、チタン、ニッケル、ステンレス鋼等の導電性を有する金属が例示できる。
正極集電体本体１４の厚みは、例えば８～４０μｍが好ましく、１０～２５μｍがより好ましい。
正極集電体本体１４の厚み及び正極集電体１１の厚みは、マイクロメータを用いて測定できる。測定器の一例としてはミツトヨ社製品名「ＭＤＨ－２５Ｍ」が挙げられる。 [Positive electrode current collector body]
The positive electrode current collector main body 14 is made of a metal material. Examples of metal materials include conductive metals such as copper, aluminum, titanium, nickel, and stainless steel.
The thickness of the positive electrode current collector main body 14 is, for example, preferably 8 to 40 μm, more preferably 10 to 25 μm.
The thickness of the positive electrode current collector main body 14 and the thickness of the positive electrode current collector 11 can be measured using a micrometer. An example of the measuring instrument is Mitutoyo's product name "MDH-25M".

［集電体被覆層］
正極集電体本体１４の表面の少なくとも一部に集電体被覆層１５が存在することが好ましい。集電体被覆層１５は導電材料を含む。
ここで、「表面の少なくとも一部」とは、正極集電体本体の表面の面積の１０％～１００％、好ましくは３０％～１００％、より好ましくは５０％～１００％を意味する。
集電体被覆層１５中の導電材料は、炭素（導電性炭素）を含むことが好ましい。炭素のみからなる導電材料がより好ましい。
集電体被覆層１５は、例えばカーボンブラック等の炭素粒子と結着材を含むコーティング層が好ましい。集電体被覆層１５の結着材は、正極活物質層１２の結着材と同様のものを例示できる。
正極集電体本体１４の表面を集電体被覆層１５で被覆した正極集電体１１は、例えば、導電材料、結着材、及び溶媒を含むスラリーを、グラビア法等の公知の塗工方法を用いて正極集電体本体１４の表面に塗工し、乾燥して溶媒を除去する方法で製造できる。 [Current collector coating layer]
It is preferable that the current collector coating layer 15 is present on at least part of the surface of the positive electrode current collector main body 14 . Current collector coating layer 15 includes a conductive material.
Here, "at least part of the surface" means 10% to 100%, preferably 30% to 100%, more preferably 50% to 100% of the surface area of the positive electrode current collector body.
The conductive material in the current collector coating layer 15 preferably contains carbon (conductive carbon). A conductive material consisting only of carbon is more preferable.
The current collector coating layer 15 is preferably a coating layer containing carbon particles such as carbon black and a binder. The binder for the current collector coating layer 15 can be exemplified by the same binder as the binder for the positive electrode active material layer 12 .
The positive electrode current collector 11 in which the surface of the positive electrode current collector main body 14 is coated with the current collector coating layer 15 is coated with a slurry containing a conductive material, a binder, and a solvent by a known coating method such as a gravure method. can be applied to the surface of the positive electrode current collector body 14 using and dried to remove the solvent.

集電体被覆層１５の厚さは、０．１～４．０μｍが好ましい。
集電体被覆層の厚さは、集電体被覆層の断面の透過電子顕微鏡（ＴＥＭ）像又は走査型電子顕微鏡（ＳＥＭ）像における被覆層の厚さを計測する方法で測定できる。集電体被覆層の厚さは均一でなくてもよい。正極集電体本体１４の表面の少なくとも一部に厚さ０．１μｍ以上の集電体被覆層が存在し、集電体被覆層の厚さの最大値が４．０μｍ以下であることが好ましい。 The thickness of the current collector coating layer 15 is preferably 0.1 to 4.0 μm.
The thickness of the current collector coating layer can be measured by measuring the thickness of the coating layer in a transmission electron microscope (TEM) image or a scanning electron microscope (SEM) image of the cross section of the current collector coating layer. The thickness of the current collector coating layer may not be uniform. A current collector coating layer having a thickness of 0.1 μm or more is present on at least a portion of the surface of the positive electrode current collector body 14, and the maximum thickness of the current collector coating layer is preferably 4.0 μm or less. .

［正極活物質層の拡がり抵抗値分布］
本実施形態において、正極活物質層の拡がり抵抗値分布において、抵抗値４．０～１２．５（ｌｏｇΩ）の頻度合計を１００％とするとき、抵抗値４．０～６．０（ｌｏｇΩ）の頻度合計は０．０～５．０％であり、０．０～４．０％が好ましく、０．０～３．０％がより好ましく、０．０～２．０％がさらに好ましい。
本明細書における正極活物質層の拡がり抵抗値分布は、正極活物質層の断面を測定対象とし、走査型拡がり抵抗顕微鏡（ＳＳＲＭ：Ｓｃａｎｎｉｎｇ Ｓｐｒｅａｄ Ｒｅｓｉｓｔａｎｃｅ Ｍｉｃｒｏｓｃｏｐｅ）を用いて、下記≪拡がり抵抗値分布の測定方法≫で測定する。 [Spreading resistance value distribution of positive electrode active material layer]
In the present embodiment, in the spreading resistance value distribution of the positive electrode active material layer, when the total frequency of resistance values 4.0 to 12.5 (log Ω) is 100%, the resistance value is 4.0 to 6.0 (log Ω). is 0.0 to 5.0%, preferably 0.0 to 4.0%, more preferably 0.0 to 3.0%, even more preferably 0.0 to 2.0%.
The spreading resistance value distribution of the positive electrode active material layer in this specification is measured using a scanning spreading resistance microscope (SSRM) using a cross section of the positive electrode active material layer as a measurement object, and the following <<spreading resistance value distribution Measurement method>>.

≪拡がり抵抗値分布の測定方法≫
ＳＳＲＭは、測定対象物にバイアス電圧を印加し、表面を導電性探針で走査し、探針直下の抵抗値（拡がり抵抗値）の分布を二次元的に計測する。
拡がり抵抗値分布の測定は、ＳＳＲＭを用い、ＤＣバイアス電圧＋２．０Ｖ、スキャンサイズ６０μｍ×６０μｍ、測定点の数（データ点数）１０２４×１０２４の条件で行い、横軸を拡がり抵抗値、縦軸を頻度とする度数分布のグラフ（拡がり抵抗値分布）を得る。
縦軸の頻度は、抵抗値が４．０ｌｏｇΩ（１×１０４Ω）以上、１２．５ｌｏｇΩ（１×１０１２．５Ω）以下である頻度（測定点の数）の合計を１００％とするときの相対頻度（単位：％、単に「頻度」ともいう）とする。 <<How to measure the spreading resistance value distribution>>
The SSRM applies a bias voltage to an object to be measured, scans the surface with a conductive probe, and two-dimensionally measures the distribution of resistance values (spreading resistance values) immediately below the probe.
The spreading resistance value distribution was measured using an SSRM under the conditions of a DC bias voltage of +2.0 V, a scan size of 60 μm×60 μm, and the number of measurement points (number of data points) of 1024×1024. A frequency distribution graph (spreading resistance value distribution) is obtained.
The frequency on the vertical axis is the total frequency (number of measurement points) at which the resistance value is 4.0 log Ω (1 × 10 4 Ω) or more and 12.5 log Ω (1 × 10 12.5 Ω) or less. relative frequency (unit: %, also simply referred to as “frequency”).

拡がり抵抗値分布において、抵抗値が４．０～６．０（ｌｏｇΩ）である頻度の合計が５．０％以下であると、非水電解質二次電池の耐熱性の向上効果に優れる。
正極活物質層の断面において、抵抗値が４．０～６．０（ｌｏｇΩ）と低い部分が存在すると、非水電解質二次電池が高温に曝されたときに、そこが活性点となって正極と電解液との副反応が生じやすいと考えられる。
抵抗値が４．０～６．０（ｌｏｇΩ）の頻度合計は、例えば、独立した導電助剤粒子（例えば独立した炭素粒子）を少なくすることによって低減できる。 If the total frequency of the resistance values of 4.0 to 6.0 (log Ω) in the spreading resistance value distribution is 5.0% or less, the effect of improving the heat resistance of the non-aqueous electrolyte secondary battery is excellent.
If there is a portion with a low resistance value of 4.0 to 6.0 (log Ω) in the cross section of the positive electrode active material layer, that portion becomes an active point when the non-aqueous electrolyte secondary battery is exposed to high temperatures. It is considered that a side reaction between the positive electrode and the electrolytic solution is likely to occur.
The frequency sum of resistance values of 4.0 to 6.0 (log Ω) can be reduced, for example, by reducing independent conductivity aid particles (eg, independent carbon particles).

拡がり抵抗値分布において、抵抗値４．０～６．０（ｌｏｇΩ）の平均頻度Ａは、抵抗値４．０～６．０（ｌｏｇΩ）の範囲のグラフを平らに均したときの頻度（％）である。具体的に、平均頻度Ａは、抵抗値４．０～６．０（ｌｏｇΩ）の範囲に存在する各測定点の抵抗値の総和を、測定点の数で割ることによって算出される。
拡がり抵抗値分布において、抵抗値６．０～９．０（ｌｏｇΩ）の平均頻度Ｂは、抵抗値６．０～９．０（ｌｏｇΩ）の範囲のグラフを平らに均したときの頻度（％）である。具体的に、平均頻度Ｂは、抵抗値６．０～９．０（ｌｏｇΩ）の範囲に存在する各測定点の抵抗値の総和を、測定点の数で割ることによって算出される。尚、ここで正極活物質層の拡がり抵抗値分布において、抵抗値６．０（ｌｏｇΩ）が存在する場合は、その頻度は平均頻度Ａの算出には考慮せず、平均頻度Ｂの算出に加える。
本実施形態において、平均頻度Ａより平均頻度Ｂが大きいこと（Ａ＜Ｂ）が好ましい。Ａ＜Ｂであると、非水電解質二次電池の耐熱性の向上効果に優れる。また非水電解質二次電池の十分な出力が得られやすい。
平均頻度Ｂは、例えば０．０５～０．５％が好ましく、０．１～０．４％がより好ましく、０．１５～０．３５％がさらに好ましい。平均頻度Ｂは、例えば、活物質被覆部として存在する導電材料を多くすることによって増大できる。
Ａ＜Ｂであるとき、Ｂ－Ａの差は０％超が好ましく、０．０５％以上がより好ましく、０．２０％以上がさらに好ましい。また、Ａに対するＢの比（Ｂ／Ａ）が、１超であることが好ましく、５以上がより好ましく、１０以上がさらに好ましい。 In the spread resistance value distribution, the average frequency A of resistance values 4.0 to 6.0 (log Ω) is the frequency (% ). Specifically, the average frequency A is calculated by dividing the sum of the resistance values of each measurement point existing in the resistance value range of 4.0 to 6.0 (logΩ) by the number of measurement points.
In the spread resistance value distribution, the average frequency B of resistance values 6.0 to 9.0 (log Ω) is the frequency (% ). Specifically, the average frequency B is calculated by dividing the sum of the resistance values of each measurement point existing in the resistance value range of 6.0 to 9.0 (logΩ) by the number of measurement points. Here, in the spreading resistance value distribution of the positive electrode active material layer, if there is a resistance value of 6.0 (log Ω), the frequency thereof is not considered in the calculation of the average frequency A, but is added to the calculation of the average frequency B. .
In this embodiment, it is preferable that the average frequency B is larger than the average frequency A (A<B). When A<B, the effect of improving the heat resistance of the non-aqueous electrolyte secondary battery is excellent. In addition, it is easy to obtain a sufficient output of the non-aqueous electrolyte secondary battery.
The average frequency B is, for example, preferably 0.05 to 0.5%, more preferably 0.1 to 0.4%, even more preferably 0.15 to 0.35%. The average frequency B can be increased, for example, by having more conductive material present as the active material coating.
When A<B, the difference BA is preferably more than 0%, more preferably 0.05% or more, and even more preferably 0.20% or more. Also, the ratio of B to A (B/A) is preferably greater than 1, more preferably 5 or more, and even more preferably 10 or more.

［導電性炭素含有量］
本実施形態において、正極活物質層１２が導電性炭素を含むことが好ましい。正極活物質層が導電性炭素を含む態様としては、下記態様１～３が挙げられる。
態様１：正極活物質層が導電助剤を含み、導電助剤が導電性炭素を含む態様。
態様２：正極活物質層が導電助剤を含み、かつ正極活物質粒子の表面の少なくとも一部に、導電材料を含む活物質被覆部が存在し、前記活物質被覆部の導電材料及び前記導電助剤の一方又は両方が導電性炭素を含む態様。
態様３：正極活物質層が導電助剤を含まず、正極活物質粒子の表面の少なくとも一部に、導電材料を含む活物質被覆部が存在し、前記活物質被覆部の導電材料が導電性炭素を含む態様。
非水電解質二次電池の耐熱性の向上効果に優れる点では態様３がより好ましい。 [Conductive carbon content]
In this embodiment, the positive electrode active material layer 12 preferably contains conductive carbon. Examples of embodiments in which the positive electrode active material layer contains conductive carbon include the following embodiments 1 to 3.
Aspect 1: A mode in which the positive electrode active material layer contains a conductive aid, and the conductive aid contains conductive carbon.
Aspect 2: The positive electrode active material layer contains a conductive aid, and an active material coating portion containing a conductive material is present on at least part of the surface of the positive electrode active material particles, and the conductive material of the active material coating portion and the conductive material Embodiments in which one or both of the auxiliaries comprise conductive carbon.
Aspect 3: The positive electrode active material layer does not contain a conductive aid, an active material coating portion containing a conductive material is present on at least part of the surface of the positive electrode active material particles, and the conductive material of the active material coating portion is conductive. Embodiments containing carbon.
Aspect 3 is more preferable in terms of the effect of improving the heat resistance of the non-aqueous electrolyte secondary battery.

正極活物質層の総質量に対して、導電性炭素の含有量は０．５質量％以上３．０質量％未満が好ましく、１．０～２．８質量％がより好ましく、１．３～２．５質量％がさらに好ましい。
正極活物質層中の導電性炭素の含有量が上記範囲の下限値以上であると良好な導電パス形成と低抵抗な特性に優れ、上限値以下であると孤立する導電性炭素が少なく、反応活性点が少ない正極活物質層が形成できる。 The content of the conductive carbon is preferably 0.5% by mass or more and less than 3.0% by mass, more preferably 1.0 to 2.8% by mass, and 1.3 to 1.3% by mass, based on the total mass of the positive electrode active material layer. 2.5% by mass is more preferred.
When the content of conductive carbon in the positive electrode active material layer is at least the lower limit of the above range, good conductive path formation and low resistance characteristics are excellent. A positive electrode active material layer having few active sites can be formed.

正極活物質層の総質量に対する導電性炭素の含有量は、正極から正極活物質層を剥がして１２０℃環境で真空乾燥した乾燥物（粉体）を測定対象物として、下記≪導電性炭素含有量の測定方法≫で測定できる。測定対象物としての乾燥物である粉体の粒子径については、後述する方法で導電性炭素の含有量の測定が適切に行える限り特に制限はない。
例えば、正極活物質層の最表面の、深さ数μｍの部分をスパチュラ等で剥がした粉体を１２０℃環境で真空乾燥させて測定対象物とすることができる。
下記≪導電性炭素含有量の測定方法≫で測定した導電性炭素の含有量は、活物質被覆部中の炭素と、導電助剤中の炭素を含む。結着材中の炭素は含まれない。分散剤中の炭素は含まれない。 The content of conductive carbon with respect to the total mass of the positive electrode active material layer is obtained by peeling the positive electrode active material layer from the positive electrode and vacuum-drying it in a 120 ° C environment. Quantity measurement method>>. There are no particular restrictions on the particle size of the powder, which is a dry matter to be measured, as long as the content of conductive carbon can be appropriately measured by the method described later.
For example, an object to be measured can be obtained by removing powder from the outermost surface of the positive electrode active material layer with a depth of several μm using a spatula or the like and vacuum-drying it in a 120° C. environment.
The content of conductive carbon measured by <<Method for Measuring Content of Conductive Carbon>> below includes carbon in the active material coating portion and carbon in the conductive aid. Carbon in the binder is not included. Carbon in the dispersant is not included.

≪導電性炭素含有量の測定方法≫
［測定方法Ａ］
測定対象物を均一に混合して試料（質量ｗ１）を量りとり、下記の工程Ａ１、工程Ａ２の手順で熱重量示差熱（ＴＧ－ＤＴＡ）測定を行い、ＴＧ曲線を得る。得られたＴＧ曲線から下記第１の重量減少量Ｍ１（単位：質量％）及び第２の重量減少量Ｍ２（単位：質量％）を求める。Ｍ２からＭ１を減算して導電性炭素の含有量（単位：質量％）を得る。
工程Ａ１：３００ｍＬ／分のアルゴン気流中において、１０℃／分の昇温速度で３０℃から６００℃まで昇温し、６００℃で１０分間保持したときの質量ｗ２から、下記式（ａ１）により第１の重量減少量Ｍ１を求める。
Ｍ１＝（ｗ１－ｗ２）／ｗ１×１００ …（ａ１）
工程Ａ２：前記工程Ａ１の直後に６００℃から１０℃／分の降温速度で降温し、２００℃で１０分間保持した後に、測定ガスをアルゴンから酸素へ完全に置換し、１００ｍＬ／分の酸素気流中において、１０℃／分の昇温速度で２００℃から１０００℃まで昇温し、１０００℃にて１０分間保持したときの質量ｗ３から、下記式（ａ２）により第２の重量減少量Ｍ２（単位：質量％）を求める。
Ｍ２＝（ｗ１－ｗ３）／ｗ１×１００ …（ａ２） <<Method for measuring conductive carbon content>>
[Measurement method A]
The object to be measured is uniformly mixed, a sample (mass w1) is weighed, thermogravimetric differential thermal analysis (TG-DTA) is performed in the following steps A1 and A2, and a TG curve is obtained. From the obtained TG curve, the following first weight reduction amount M1 (unit: mass %) and second weight reduction amount M2 (unit: mass %) are determined. Subtract M1 from M2 to obtain the content of conductive carbon (unit: % by mass).
Step A1: In an argon stream of 300 mL/min, the temperature is raised from 30° C. to 600° C. at a rate of temperature increase of 10° C./min and held at 600° C. for 10 minutes. A first weight reduction amount M1 is obtained.
M1=(w1-w2)/w1×100 (a1)
Step A2: Immediately after step A1, the temperature is lowered from 600° C. at a rate of 10° C./min, held at 200° C. for 10 minutes, and then the measurement gas is completely replaced from argon to oxygen with an oxygen flow of 100 mL/min. Inside, the temperature is increased from 200 ° C. to 1000 ° C. at a temperature increase rate of 10 ° C./min, and the mass w3 when held at 1000 ° C. for 10 minutes is calculated by the following formula (a2) to obtain the second weight reduction amount M2 ( Unit: % by mass).
M2=(w1-w3)/w1×100 (a2)

［測定方法Ｂ］
測定対象物を均一に混合して試料を０．０００１ｍｇ精秤し、下記の燃焼条件で試料を燃焼し、発生した二酸化炭素をＣＨＮ元素分析装置により定量し、試料に含まれる全炭素量Ｍ３（単位：質量％）を測定する。また、前記測定方法Ａの工程Ａ１の手順で第１の重量減少量Ｍ１を求める。Ｍ３からＭ１を減算して導電性炭素の含有量（単位：質量％）を得る。
［燃焼条件］
燃焼炉：１１５０℃
還元炉：８５０℃
ヘリウム流量：２００ｍＬ／分
酸素流量：２５～３０ｍＬ／分 [Measurement method B]
The object to be measured is uniformly mixed and 0.0001 mg of the sample is accurately weighed, the sample is burned under the following combustion conditions, the carbon dioxide generated is quantified by a CHN elemental analyzer, and the total carbon content M3 ( Unit: % by mass). In addition, the first weight reduction amount M1 is obtained by the procedure of step A1 of the measuring method A described above. Subtract M1 from M3 to obtain the conductive carbon content (unit: % by mass).
[Combustion conditions]
Combustion furnace: 1150°C
Reduction furnace: 850°C
Helium flow rate: 200 mL/min Oxygen flow rate: 25-30 mL/min

［測定方法Ｃ］
上記測定方法Ｂと同様にして、試料に含まれる全炭素量Ｍ３（単位：質量％）を測定する。また、下記の方法で結着材由来の炭素の含有量Ｍ４（単位：質量％）を求める。Ｍ３からＭ４を減算して導電性炭素の含有量（単位：質量％）を得る。
結着材がポリフッ化ビニリデン（ＰＶＤＦ：モノマー（ＣＨ２ＣＦ２）の分子量６４）である場合は、管状式燃焼法による燃焼イオンクロマトグラフィーにより測定されたフッ化物イオン（Ｆ－）の含有量（単位：質量％）、ＰＶＤＦを構成するモノマーのフッ素の原子量（１９）、及びＰＶＤＦを構成する炭素の原子量（１２）から以下の式で計算することができる。
ＰＶＤＦの含有量（単位：質量％）＝フッ化物イオンの含有量（単位：質量％）×６４／３８
ＰＶＤＦ由来の炭素の含有量Ｍ４（単位：質量％）＝フッ化物イオンの含有量（単位：質量％）×１２／１９
結着材がポリフッ化ビニリデンであることは、試料、又は試料をＮ，Ｎ－ジメチルホルムアミド（ＤＭＦ）溶媒により抽出した液体をフーリエ変換赤外スペクトル（ＦＴ－ＩＲ）測定し、Ｃ－Ｆ結合由来の吸収を確認する方法で確かめることができる。同様に１９Ｆ－ＮＭＲ測定でも確かめることができる。
結着材がＰＶＤＦ以外と同定された場合は、その分子量に相当する結着材の含有量（単位：質量％）および炭素の含有量（単位：質量％）を求めることで、結着材由来の炭素量Ｍ４を算出できる。
分散剤が含まれる場合は、前記Ｍ３からＭ４を減算し、さらに分散剤由来の炭素量を減算して導電性炭素の含有量（単位：質量％）を得ることができる。 [Measurement method C]
The total carbon content M3 (unit: % by mass) contained in the sample is measured in the same manner as in the measurement method B above. Also, the binder-derived carbon content M4 (unit: % by mass) is determined by the following method. Subtract M4 from M3 to obtain the conductive carbon content (unit: % by mass).
When the binder is polyvinylidene fluoride (PVDF: monomer (CH 2 CF 2 ) molecular weight 64), the content of fluoride ions (F − ) measured by combustion ion chromatography using a tubular combustion method ( Unit: % by mass), the fluorine atomic weight (19) of the monomer constituting PVDF, and the atomic weight (12) of carbon constituting PVDF by the following formula.
PVDF content (unit: mass%) = fluoride ion content (unit: mass%) x 64/38
PVDF-derived carbon content M4 (unit: mass%) = fluoride ion content (unit: mass%) x 12/19
The fact that the binder is polyvinylidene fluoride is obtained by measuring the sample or the liquid obtained by extracting the sample with an N,N-dimethylformamide (DMF) solvent by Fourier transform infrared spectrum (FT-IR), can be confirmed by a method for confirming the absorption of It can also be confirmed by 19 F-NMR measurement.
If the binder is identified to be other than PVDF, the content of the binder (unit: mass %) corresponding to the molecular weight and the content of carbon (unit: mass %) of carbon content M4 can be calculated.
When a dispersant is included, the content of conductive carbon (unit: mass %) can be obtained by subtracting M4 from M3 and further subtracting the amount of carbon derived from the dispersant.

正極活物質の組成などに応じて、［測定方法Ａ］～［測定方法Ｃ］から適切な方法を選択して導電性炭素の含有量を求めることができるが、汎用性などの観点から、［測定方法Ｂ］により導電性炭素の含有量を求めることが好ましい。
これらの手法は下記複数の公知文献に記載されている。
東レリサーチセンター Ｔｈｅ ＴＲＣ Ｎｅｗｓ Ｎｏ．１１７ （Ｓｅｐ．２０１３）第３４～３７頁、［２０２１年２月１０日検索］、インターネット＜https://www.toray-research.co.jp/technical-info/trcnews/pdf/TRC117(34-37).pdf＞
東ソー分析センター 技術レポート Ｎｏ．Ｔ１０１９ ２０１７．０９．２０、［２０２１年２月１０日検索］、インターネット＜http://www.tosoh-arc.co.jp/techrepo/files/tarc00522/T1719N.pdf＞ Depending on the composition of the positive electrode active material, etc., the content of conductive carbon can be determined by selecting an appropriate method from [Measurement method A] to [Measurement method C]. It is preferable to determine the content of conductive carbon by measuring method B].
These techniques are described in the following publications.
Toray Research Center The TRC News No. 117 (Sep. 2013) pp. 34-37, [searched on February 10, 2021], Internet <https://www.toray-research.co.jp/technical-info/trcnews/pdf/TRC117(34- 37).pdf＞
Tosoh Analysis Center Technical Report No. T1019 2017.09.20, [searched on February 10, 2021], Internet <http://www.tosoh-arc.co.jp/techrepo/files/tarc00522/T1719N.pdf>

≪導電性炭素の分析方法≫
正極活物質の活物質被覆部を構成する導電性炭素と、導電助剤である導電性炭素は、以下の分析方法で区別できる。
例えば、正極活物質層中の粒子を透過電子顕微鏡電子エネルギー損失分光法（ＴＥＭ－ＥＥＬＳ）により分析し、粒子表面近傍にのみ２９０ｅＶ付近の炭素由来のピークが存在する粒子は正極活物質であり、粒子内部にまで炭素由来のピークが存在する粒子は導電助剤と判定することができる。ここで「粒子表面近傍」とは、粒子表面からの深さが、約１００ｎｍまでの領域を意味し、「粒子内部」とは前記粒子表面近傍よりも内側の領域を意味する。
他の方法としては、正極活物質層中の粒子をラマン分光によりマッピング解析し、炭素由来のＧ－ｂａｎｄとＤ－ｂａｎｄ、及び正極活物質由来の酸化物結晶のピークが同時に観測された粒子は正極活物質であり、Ｇ－ｂａｎｄとＤ－ｂａｎｄのみが観測された粒子は導電助剤と判定することができる。
さらに他の方法としては、拡がり抵抗顕微鏡（ＳＳＲＭ：Ｓｃａｎｎｉｎｇ Ｓｐｒｅａｄ Ｒｅｓｉｓｔａｎｃｅ Ｍｉｃｒｏｓｃｏｐｅ）により、正極活物質層の断面を観察し、粒子表面に粒子内部より抵抗が低い部分が存在する場合、抵抗が低い部分は活物質被覆部に存在する導電性炭素であると判定できる。そのような粒子以外に独立して存在し、かつ抵抗が低い部分は導電助剤であると判定することができる。
なお、不純物として考えられる微量な炭素や、製造時に正極活物質の表面から意図せず剥がれた微量な炭素などは、導電助剤と判定しない。
これらの方法を用いて、炭素材料からなる導電助剤が正極活物質層に含まれるか否かを確認することができる。 <<Method for analyzing conductive carbon>>
The conductive carbon that constitutes the active material coating portion of the positive electrode active material and the conductive carbon that is the conductive aid can be distinguished by the following analysis method.
For example, the particles in the positive electrode active material layer are analyzed by transmission electron microscope electron energy loss spectroscopy (TEM-EELS), and particles having a carbon-derived peak near 290 eV only in the vicinity of the particle surface are positive electrode active materials, Particles in which carbon-derived peaks are present even inside the particles can be determined to be conductive aids. Here, "near the particle surface" means a region up to about 100 nm deep from the particle surface, and "inside the particle" means a region inside the vicinity of the particle surface.
As another method, the particles in the positive electrode active material layer are subjected to mapping analysis by Raman spectroscopy. Particles that are positive electrode active materials and in which only the G-band and D-band are observed can be determined as conductive aids.
As yet another method, a scanning spread resistance microscope (SSRM) is used to observe the cross section of the positive electrode active material layer. It can be determined that it is the conductive carbon present in the active material coating portion. It can be determined that a portion that exists independently and has a low resistance other than such particles is the conductive aid.
A small amount of carbon considered as an impurity, a small amount of carbon unintentionally peeled off from the surface of the positive electrode active material during production, and the like are not determined to be conductive aids.
Using these methods, it is possible to confirm whether or not the positive electrode active material layer contains a conductive aid made of a carbon material.

［正極活物質層の体積密度］
本実施形態において、正極活物質層１２の体積密度は２．２０～２．７０ｇ／ｃｍ３が好ましく、２．２５～２．５０ｇ／ｃｍ３がより好ましい。
正極活物質層の体積密度は、例えば以下の測定方法により測定できる。
正極１及び正極集電体１１の厚みをそれぞれマイクロゲージで測定し、これらの差から正極活物質層１２の厚みを算出する。正極１及び正極集電体１１の厚みは、それぞれ任意の５点以上で測定した値の平均値とする。正極集電体１１の厚みとして、後述の正極集電体露出部１３の厚みを用いてよい。
正極１を所定の面積となるように打ち抜いた測定試料の質量を測定し、予め測定した正極集電体１１の質量を差し引いて、正極活物質層１２の質量を算出する。
下記式（１）に基づいて、正極活物質層１２の体積密度を算出する。
体積密度（単位：ｇ／ｃｍ３）＝正極活物質層の質量（単位：ｇ）／［（正極活物質層の厚み（単位：ｃｍ）×測定試料の面積（単位：ｃｍ２）］・・・（１） [Volume Density of Positive Electrode Active Material Layer]
In the present embodiment, the volume density of the positive electrode active material layer 12 is preferably 2.20-2.70 g/cm 3 , more preferably 2.25-2.50 g/cm 3 .
The volume density of the positive electrode active material layer can be measured, for example, by the following measuring method.
The thicknesses of the positive electrode 1 and the positive electrode current collector 11 are each measured with a microgauge, and the thickness of the positive electrode active material layer 12 is calculated from the difference between them. The thickness of the positive electrode 1 and the positive electrode current collector 11 is the average value of the values measured at five or more arbitrary points. As the thickness of the positive electrode current collector 11, the thickness of the positive electrode current collector exposed portion 13, which will be described later, may be used.
The mass of a measurement sample obtained by punching out the positive electrode 1 to have a predetermined area is measured, and the mass of the positive electrode active material layer 12 is calculated by subtracting the pre-measured mass of the positive electrode current collector 11 .
The volume density of the positive electrode active material layer 12 is calculated based on the following formula (1).
Volume density (unit: g/cm 3 )=mass of positive electrode active material layer (unit: g)/[(thickness of positive electrode active material layer (unit: cm)×area of measurement sample (unit: cm 2 )]...・(1)

＜正極の製造方法＞
本実施形態の正極１の製造方法は、正極活物質を含む正極製造用組成物を調製する組成物調製工程と、正極製造用組成物を正極集電体１１上に塗工する塗工工程を有する。
例えば、正極活物質及び溶媒を含む正極製造用組成物を、正極集電体１１上に塗工し、乾燥し溶媒を除去して正極活物質層１２を形成する方法で正極１を製造できる。正極製造用組成物は導電助剤を含んでもよい。正極製造用組成物は結着材を含んでもよい。製造用組成物は分散剤を含んでもよい。
正極集電体１１上に正極活物質層１２を形成した積層物を、２枚の平板状冶具の間に挟み、厚み方向に均一に加圧する方法で、正極活物質層１２の厚みを調整できる。例えば、ロールプレス機を用いて加圧（圧延）する方法を使用できる。 <Manufacturing method of positive electrode>
The method for manufacturing the positive electrode 1 of the present embodiment includes a composition preparation step of preparing a positive electrode manufacturing composition containing a positive electrode active material, and a coating step of applying the positive electrode manufacturing composition onto the positive electrode current collector 11. have.
For example, the positive electrode 1 can be manufactured by applying a positive electrode manufacturing composition containing a positive electrode active material and a solvent onto the positive electrode current collector 11 and drying it to remove the solvent to form the positive electrode active material layer 12 . The composition for positive electrode production may contain a conductive aid. The positive electrode manufacturing composition may contain a binder. The manufacturing composition may contain a dispersant.
The thickness of the positive electrode active material layer 12 can be adjusted by a method in which a laminate in which the positive electrode active material layer 12 is formed on the positive electrode current collector 11 is sandwiched between two flat jigs and is evenly pressed in the thickness direction. . For example, a method of pressing (rolling) using a roll press can be used.

正極製造用組成物の溶媒は非水系溶媒が好ましい。例えば、メタノール、エタノール、１－プロパノール、２－プロパノール等のアルコール；Ｎ－メチルピロリドン、Ｎ，Ｎ－ジメチルホルムアミド等の鎖状又は環状アミド；アセトン等のケトンが挙げられる。溶媒は１種でもよく、２種以上を併用してもよい。 A non-aqueous solvent is preferable as the solvent for the positive electrode-manufacturing composition. Examples include alcohols such as methanol, ethanol, 1-propanol and 2-propanol; linear or cyclic amides such as N-methylpyrrolidone and N,N-dimethylformamide; and ketones such as acetone. One type of solvent may be used, or two or more types may be used in combination.

＜非水電解質二次電池＞
図２に示す本実施形態の非水電解質二次電池１０は、本実施形態の非水電解質二次電池用正極１と、負極３と、非水電解質とを備える。さらにセパレータ２を備えてもよい。図中符号５は外装体である。
本実施形態において、正極１は、板状の正極集電体１１と、その両面上に設けられた正極活物質層１２と有する。正極活物質層１２は正極集電体１１の表面の一部に存在する。正極集電体１１の表面の縁部は、正極活物質層１２が存在しない正極集電体露出部１３である。正極集電体露出部１３の任意の箇所に、図示しない端子用タブが電気的に接続する。
負極３は、板状の負極集電体３１と、その両面上に設けられた負極活物質層３２とを有する。負極活物質層３２は負極集電体３１の表面の一部に存在する。負極集電体３１の表面の縁部は、負極活物質層３２が存在しない負極集電体露出部３３である。負極集電体露出部３３の任意の箇所に、図示しない端子用タブが電気的に接続する。
正極１、負極３およびセパレータ２の形状は特に限定されない。例えば平面視矩形状でもよい。
本実施形態の非水電解質二次電池１０は、例えば、正極１と負極３を、セパレータ２を介して交互に積層した電極積層体を作製し、電極積層体をアルミラミネート袋等の外装体（筐体）５に封入し、非水電解質（図示せず）を注入して密閉する方法で製造できる。
図２では、代表的に、負極／セパレータ／正極／セパレータ／負極の順に積層した構造を示しているが、電極の数は適宜変更できる。正極１は１枚以上あればよく、得ようとする電池容量に応じて任意の数の正極１を用いることができる。負極３及びセパレータ２は、正極１の数より１枚多く用い、最外層が負極３となるように積層する。 <Non-aqueous electrolyte secondary battery>
A non-aqueous electrolyte secondary battery 10 of the present embodiment shown in FIG. 2 includes the positive electrode 1 for non-aqueous electrolyte secondary batteries of the present embodiment, a negative electrode 3, and a non-aqueous electrolyte. Further, a separator 2 may be provided. Reference numeral 5 in the figure is an exterior body.
In this embodiment, the positive electrode 1 has a plate-like positive electrode current collector 11 and positive electrode active material layers 12 provided on both sides thereof. The positive electrode active material layer 12 exists on part of the surface of the positive electrode current collector 11 . An edge portion of the surface of the positive electrode current collector 11 is a positive electrode current collector exposed portion 13 where the positive electrode active material layer 12 does not exist. A terminal tab (not shown) is electrically connected to an arbitrary portion of the positive electrode current collector exposed portion 13 .
The negative electrode 3 has a plate-like negative electrode current collector 31 and negative electrode active material layers 32 provided on both sides thereof. The negative electrode active material layer 32 exists on part of the surface of the negative electrode current collector 31 . An edge portion of the surface of the negative electrode current collector 31 is a negative electrode current collector exposed portion 33 where the negative electrode active material layer 32 does not exist. A terminal tab (not shown) is electrically connected to an arbitrary portion of the negative electrode current collector exposed portion 33 .
The shapes of the positive electrode 1, the negative electrode 3 and the separator 2 are not particularly limited. For example, it may be rectangular in plan view.
The non-aqueous electrolyte secondary battery 10 of the present embodiment is produced, for example, by fabricating an electrode laminate in which the positive electrode 1 and the negative electrode 3 are alternately laminated with the separator 2 interposed therebetween, and the electrode laminate is packaged in an outer package such as an aluminum laminate bag ( It can be manufactured by a method of enclosing in a housing 5, injecting a non-aqueous electrolyte (not shown), and sealing.
FIG. 2 typically shows a structure in which negative electrodes/separators/positive electrodes/separators/negative electrodes are laminated in this order, but the number of electrodes can be changed as appropriate. One or more positive electrodes 1 are sufficient, and any number of positive electrodes 1 can be used according to the battery capacity to be obtained. One more negative electrode 3 and separator 2 than the number of positive electrodes 1 are used, and they are laminated so that the negative electrode 3 is the outermost layer.

［負極］
負極活物質層３２は負極活物質を含む。さらに結着材を含んでもよい。さらに導電助剤を含んでもよい。負極活物質の形状は、粒子状が好ましい。
負極３は、例えば、負極活物質、結着材、及び溶媒を含む負極製造用組成物を調製し、これを負極集電体３１上に塗工し、乾燥し溶媒を除去して負極活物質層３２を形成する方法で製造できる。負極製造用組成物は導電助剤を含んでもよい。 [Negative electrode]
The negative electrode active material layer 32 contains a negative electrode active material. Furthermore, a binding material may be included. Further, it may contain a conductive aid. The shape of the negative electrode active material is preferably particulate.
For the negative electrode 3, for example, a negative electrode manufacturing composition containing a negative electrode active material, a binder, and a solvent is prepared, the negative electrode current collector 31 is coated with the composition, and the solvent is removed by drying to remove the negative electrode active material. It can be manufactured by any method that forms layer 32 . The negative electrode production composition may contain a conductive aid.

負極活物質及び導電助剤としては、例えば炭素材料、チタン酸リチウム（ＬＴＯ）、シリコン、一酸化シリコン等が挙げられる。炭素材料としては、ケッチェンブラック、アセチレンブラック等のカーボンブラック、グラファイト、グラフェン、ハードカーボン、カーボンナノチューブ（ＣＮＴ）等が挙げられる。負極活物質及び導電助剤は、それぞれ１種でもよく２種以上を併用してもよい。 Examples of negative electrode active materials and conductive aids include carbon materials, lithium titanate (LTO), silicon, and silicon monoxide. Examples of carbon materials include carbon black such as ketjen black and acetylene black, graphite, graphene, hard carbon, and carbon nanotube (CNT). Each of the negative electrode active material and the conductive aid may be used alone or in combination of two or more.

負極集電体３１の材料は、上記した正極集電体１１の材料と同様のものを例示できる。
負極製造用組成物中の結着材としては、ポリアクリル酸（ＰＡＡ）、ポリアクリル酸リチウム（ＰＡＡＬｉ）、ポリフッ化ビニリデン（ＰＶＤＦ）、ポリフッ化ビニリデン－六フッ化プロピレン共重合体（ＰＶＤＦ－ＨＦＰ）、スチレンブタジエンゴム（ＳＢＲ）、ポリビニルアルコール（ＰＶＡ）、ポリエチレンオキサイド（ＰＥＯ）、ポリエチレングリコール（ＰＥＧ）、カルボキシメチルセルロース（ＣＭＣ）、ポリアクリルニトリル（ＰＡＮ）、ポリイミド（ＰＩ）等が例示できる。結着材は１種でもよく２種以上を併用してもよい。
負極製造用組成物中の溶媒としては、水、有機溶媒が例示できる。有機溶媒としては、メタノール、エタノール、１－プロパノール、２－プロパノール等のアルコール；Ｎ－メチルピロリドン（ＮＭＰ）、Ｎ，Ｎ－ジメチルホルムアミド（ＤＭＦ）等の鎖状又は環状アミド；アセトン等のケトンが例示できる。溶媒は１種でもよく２種以上を併用してもよい。 The material of the negative electrode current collector 31 can be exemplified by the same material as the positive electrode current collector 11 described above.
Binders in the negative electrode production composition include polyacrylic acid (PAA), lithium polyacrylate (PAALi), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-propylene hexafluoride copolymer (PVDF-HFP ), styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), polyethylene oxide (PEO), polyethylene glycol (PEG), carboxymethylcellulose (CMC), polyacrylonitrile (PAN), polyimide (PI), and the like. One type of binder may be used, or two or more types may be used in combination.
Examples of the solvent in the negative electrode-producing composition include water and organic solvents. Organic solvents include alcohols such as methanol, ethanol, 1-propanol and 2-propanol; linear or cyclic amides such as N-methylpyrrolidone (NMP) and N,N-dimethylformamide (DMF); and ketones such as acetone. I can give an example. The solvent may be used alone or in combination of two or more.

負極活物質層３２の総質量に対して、負極活物質及び導電助剤の合計の含有量は８０．０～９９．９質量％が好ましく、８５．０～９８．０質量％がより好ましい。 The total content of the negative electrode active material and the conductive aid is preferably 80.0 to 99.9 mass %, more preferably 85.0 to 98.0 mass %, relative to the total mass of the negative electrode active material layer 32 .

［セパレータ］
セパレータ２を負極３と正極１との間に配置して短絡等を防止する。セパレータ２は、後述する非水電解質を保持してもよい。
セパレータ２としては、特に限定されず、多孔性の高分子膜、不織布、ガラスファイバー等が例示できる。
セパレータ２の一方又は両方の表面上に絶縁層を設けてもよい。絶縁層は、絶縁性微粒子を絶縁層用結着材で結着した多孔質構造を有する層が好ましい。 [Separator]
A separator 2 is arranged between the negative electrode 3 and the positive electrode 1 to prevent short circuit or the like. The separator 2 may hold a non-aqueous electrolyte, which will be described later.
The separator 2 is not particularly limited, and can be exemplified by porous polymer membranes, non-woven fabrics, glass fibers, and the like.
An insulating layer may be provided on one or both surfaces of the separator 2 . The insulating layer is preferably a layer having a porous structure in which insulating fine particles are bound with an insulating layer binder.

セパレータ２は、各種可塑剤、酸化防止剤、難燃剤を含んでもよい。
酸化防止剤としては、ヒンダードフェノール系酸化防止剤、モノフェノール系酸化防止剤、ビスフェノール系酸化防止剤、ポリフェノール系酸化防止剤等のフェノール系酸化防止剤；ヒンダードアミン系酸化防止剤；リン系酸化防止剤；イオウ系酸化防止剤；ベンゾトリアゾール系酸化防止剤；ベンゾフェノン系酸化防止剤；トリアジン系酸化防止剤；サルチル酸エステル系酸化防止剤等が例示できる。フェノール系酸化防止剤、リン系酸化防止剤が好ましい。 The separator 2 may contain various plasticizers, antioxidants and flame retardants.
Antioxidants include phenolic antioxidants such as hindered phenolic antioxidants, monophenolic antioxidants, bisphenolic antioxidants, and polyphenolic antioxidants; hindered amine antioxidants; phosphorus antioxidants. benzotriazole-based antioxidants; benzophenone-based antioxidants; triazine-based antioxidants; salicylic acid ester-based antioxidants, and the like. Phenolic antioxidants and phosphorus antioxidants are preferred.

［非水電解質］
非水電解質は正極１と負極３との間を満たす。例えば、リチウムイオン二次電池、電気二重層キャパシタ等において公知の非水電解質を使用できる。
非水電解質として、有機溶媒に電解質塩を溶解した非水電解液が好ましい。 [Non-aqueous electrolyte]
A non-aqueous electrolyte fills between the positive electrode 1 and the negative electrode 3 . For example, known non-aqueous electrolytes can be used in lithium ion secondary batteries, electric double layer capacitors and the like.
As the non-aqueous electrolyte, a non-aqueous electrolytic solution obtained by dissolving an electrolyte salt in an organic solvent is preferable.

有機溶媒は、高電圧に対する耐性を有するものが好ましい。例えば、エチレンカーボネート、プロピレンカーボネート、ジメチルカーボネート、ジエチルカーボネート、エチルメチルカーボネート、γ－ブチロラクトン、スルホラン、ジメチルスルホキシド、アセトニトリル、ジメチルホルムアミド、ジメチルアセトアミド、１，２－ジメトキシエタン、１，２－ジエトキシエタン、テトロヒドラフラン、２－メチルテトラヒドロフラン、ジオキソラン、メチルアセテート等の極性溶媒、又はこれら極性溶媒の２種類以上の混合物が挙げられる。 The organic solvent preferably has resistance to high voltage. For example, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, sulfolane, dimethyl sulfoxide, acetonitrile, dimethylformamide, dimethylacetamide, 1,2-dimethoxyethane, 1,2-diethoxyethane, Polar solvents such as tetrahydrafuran, 2-methyltetrahydrofuran, dioxolane, methyl acetate, or mixtures of two or more of these polar solvents are included.

電解質塩は、特に限定されず、例えばＬｉＣｌＯ４、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＡｓＦ６、ＬｉＣＦ６、ＬｉＣＦ３ＣＯ２、ＬｉＰＦ６ＳＯ３、ＬｉＮ（ＳＯ２Ｆ）２、ＬｉＮ（ＳＯ２ＣＦ３）２、Ｌｉ（ＳＯ２ＣＦ２ＣＦ３）２、ＬｉＮ（ＣＯＣＦ３）２、ＬｉＮ（ＣＯＣＦ２ＣＦ３）２等のリチウムを含む塩、又はこれら塩の２種以上の混合物が挙げられる。 The electrolyte salt is not particularly limited, and examples thereof include LiClO 4 , LiPF 6 , LiBF 4 , LiAsF 6 , LiCF 6 , LiCF 3 CO 2 , LiPF 6 SO 3 , LiN(SO 2 F) 2 and LiN(SO 2 CF 3 ). 2 , Li( SO2CF2CF3 ) 2 , LiN( COCF3 ) 2 , LiN( COCF2CF3 ) 2 , or a mixture of two or more of these salts.

本実施形態の非水電解質二次電池は、産業用、民生用、自動車用、住宅用等、各種用途のリチウムイオン二次電池として使用できる。
本実施形態の非水電解質二次電池の使用形態は特に限定されない。例えば、複数個の非水電解質二次電池を直列又は並列に接続して構成した電池モジュール、電気的に接続した複数個の電池モジュールと電池制御システムとを備える電池システム等に用いることができる。
電池システムの例としては、電池パック、定置用蓄電池システム、自動車の動力用蓄電池システム、自動車の補機用蓄電池システム、非常電源用蓄電池システム等が挙げられる。 The non-aqueous electrolyte secondary battery of the present embodiment can be used as a lithium ion secondary battery for various uses such as industrial use, consumer use, automobile use, and residential use.
The mode of use of the non-aqueous electrolyte secondary battery of this embodiment is not particularly limited. For example, it can be used in a battery module configured by connecting a plurality of nonaqueous electrolyte secondary batteries in series or in parallel, a battery system including a plurality of electrically connected battery modules and a battery control system, and the like.
Examples of battery systems include battery packs, stationary storage battery systems, automotive power storage battery systems, automotive auxiliary equipment storage battery systems, and emergency power supply storage battery systems.

後述の実施例に示されるように、本発明によれば非水電解質二次電池の耐熱性を向上できる。例えば、８０℃、２０日間の貯蔵前後の１Ｃ出力試験において、５０％以上、好ましくは６０％以上の出力維持率を達成できる。
したがって、従来は非水電解質二次電池を使用することが困難であった高温環境においても、非水電解質二次電池を使用しやすくなる。例えば、車両のエンジンルーム内で使用される鉛蓄電池の代替品としての、非水電解質二次電池の提供が可能となる。 As shown in the examples below, the present invention can improve the heat resistance of non-aqueous electrolyte secondary batteries. For example, in a 1C output test before and after storage at 80°C for 20 days, an output retention rate of 50% or more, preferably 60% or more can be achieved.
Therefore, it becomes easy to use the non-aqueous electrolyte secondary battery even in a high-temperature environment where it has been difficult to use the non-aqueous electrolyte secondary battery. For example, it is possible to provide a non-aqueous electrolyte secondary battery as a substitute for a lead-acid battery used in the engine room of a vehicle.

－ 第２の実施形態 －
本発明の第２の実施形態に係る非水電解質二次電池用正極１は、集電体１１と、前記集電体１１上に存在する正極活物質層１２を有し、前記正極活物質層１２が正極活物質及び導電性炭素材料を含み、前記正極活物質層１２の総質量に対して、抵抗率が０．１０Ω・ｃｍ以下である低抵抗導電性炭素材料の含有量が０．５質量％以下である。 - Second Embodiment -
A positive electrode 1 for a non-aqueous electrolyte secondary battery according to a second embodiment of the present invention has a current collector 11 and a positive electrode active material layer 12 present on the current collector 11, and the positive electrode active material layer 12 contains a positive electrode active material and a conductive carbon material, and the content of the low resistance conductive carbon material having a resistivity of 0.10 Ω·cm or less is 0.5 with respect to the total mass of the positive electrode active material layer 12 % by mass or less.

本発明者等は、非水電解質二次電池の急速充放電による劣化現象について検討した。急速充放電による電池の劣化は、電解液の分解およびその分解生成物と電極との反応によって抵抗成分が上昇することにより進行する。電解液の分解のメカニズムは従来十分に解析がなされていなかったが、本発明者らは、抵抗率が低い導電性炭素材料と電解液との反応が、劣化反応の起点になっていることを知見し、本発明に至った。
上記構成を有する非水電解質二次電池用正極１は、非水電解質二次電池の急速充放電サイクル特性を向上できる。
以下に具体的に説明する。 The present inventors have studied the deterioration phenomenon of non-aqueous electrolyte secondary batteries due to rapid charging and discharging. Degradation of the battery due to rapid charging and discharging progresses as the resistance component increases due to the decomposition of the electrolyte and the reaction between the decomposition product and the electrode. Although the decomposition mechanism of the electrolytic solution has not been sufficiently analyzed in the past, the present inventors have found that the reaction between the conductive carbon material with low resistivity and the electrolytic solution is the starting point of the deterioration reaction. This discovery led to the present invention.
The positive electrode 1 for a nonaqueous electrolyte secondary battery having the above configuration can improve the rapid charge/discharge cycle characteristics of the nonaqueous electrolyte secondary battery.
A specific description will be given below.

［正極活物質層］
正極活物質層１２は正極活物質粒子を含む。
正極活物質層１２は、さらに結着材を含むことが好ましい。
正極活物質層１２は、さらに導電助剤を含んでもよい。本明細書において、「導電助剤」という用語は、正極活物質層を形成するにあたって正極活物質粒子と混合する、粒状、繊維状などの形状を有する導電材料であって、正極活物質粒子を繋ぐ形で正極活物質層中に存在させる導電材料を指す。
正極活物質層１２は、さらに分散剤を含んでもよい。
正極活物質層１２の総質量に対して、正極活物質粒子の含有量は８０．０～９９．９質量％が好ましく、９０～９９．５質量％がより好ましい。 [Positive electrode active material layer]
The positive electrode active material layer 12 contains positive electrode active material particles.
The positive electrode active material layer 12 preferably further contains a binder.
The positive electrode active material layer 12 may further contain a conductive aid. As used herein, the term “conductive aid” refers to a conductive material having a shape such as a granular or fibrous shape, which is mixed with the positive electrode active material particles in forming the positive electrode active material layer. It refers to a conductive material present in the positive electrode active material layer in a form of connection.
The positive electrode active material layer 12 may further contain a dispersant.
The content of the positive electrode active material particles is preferably 80.0 to 99.9% by mass, more preferably 90 to 99.5% by mass, based on the total mass of the positive electrode active material layer 12 .

正極活物質層の厚み（正極集電体の両面上に正極活物質層が存在する場合、両面の合計）は３０～５００μｍであることが好ましく、４０～４００μｍであることがより好ましく、５０～３００μｍであることが特に好ましい。正極活物質層の厚みが上記範囲の下限値以上であると、電池としてのエネルギー密度が高くなりやすく、上記範囲の上限値以下であると、正極活物質層の剥離強度が高く、充放電時に剥がれを抑制できる。 The thickness of the positive electrode active material layer (when the positive electrode active material layer is present on both sides of the positive electrode current collector, the total thickness of both surfaces) is preferably 30 to 500 μm, more preferably 40 to 400 μm, and 50 to 500 μm. 300 μm is particularly preferred. When the thickness of the positive electrode active material layer is at least the lower limit of the above range, the energy density of the battery tends to be high. Peeling can be suppressed.

［正極活物質粒子］
正極活物質粒子は正極活物質からなる粒子本体を含む。粒子本体の表面の少なくとも一部に、導電材料である活物質被覆部が存在することが好ましい（活物質被覆部を有する正極活物質粒子を、以下、「被覆粒子」と称することもある）。電池容量、サイクル特性により優れる点から、粒子本体の表面全体が導電材料で被覆されていることがより好ましい。
ここで、「粒子本体の表面の少なくとも一部」とは、活物質被覆部が、粒子本体の外表面全体の面積の５０％以上、好ましくは７０％以上、より好ましくは９０％以上、特に好ましくは１００％を覆っていることを意味する。なお、この割合（％）（以下、「被覆率」と称することもある。）は、正極活物質層中に存在する正極活物質粒子全体についての平均値であり、この平均値が上記下限値以上となる限り、活物質被覆部を有しない、すなわち粒子本体のみからなる正極活物質粒子が微量に存在することを排除するものではない。活物質被覆部を有しない正極活物質粒子が正極活物質層中に存在する場合、その量は、正極活物質層中に存在する正極活物質粒子全体の量に対して、好ましくは３０質量％以下であり、より好ましくは２０質量％以下であり、特に好ましくは１０質量％以下である。
前記被覆率は次の様な方法により測定することができる。 まず、正極活物質層中の粒子を、透過電子顕微鏡を用いたエネルギー分散型Ｘ線分光法（ＴＥＭ－ＥＤＸ）により分析する。具体的には、ＴＥＭ画像における正極活物質粒子の外周部をＥＤＸで元素分析する。元素分析は炭素について行い、正極活物質粒子を被覆している炭素を特定する。炭素の被覆部が１ｎｍ以上の厚さである箇所を被覆部分とし、観察した正極活物質粒子の全周に対して被覆部分の割合を求め、これを被覆率とすることができる。測定は例えば、１０個の正極活物質粒子について行い、これらの平均値とすることができる。
また、前記活物質被覆部は、正極活物質のみから構成される粒子（以下、「芯部」と称することもある。）の表面上に直接形成された厚み１ｎｍ～１００ｎｍ、好ましくは５ｎｍ～５０ｎｍの層であり、この厚みは上述した被覆率の測定に用いるＴＥＭ－ＥＤＸによって確認することができる。 [Positive electrode active material particles]
The positive electrode active material particles contain a particle body made of a positive electrode active material. It is preferable that an active material coating portion, which is a conductive material, is present on at least part of the surface of the particle body (positive electrode active material particles having an active material coating portion may be hereinafter referred to as “coated particles”). From the viewpoint of better battery capacity and cycle characteristics, it is more preferable that the entire surface of the particle body is coated with a conductive material.
Here, "at least part of the surface of the particle body" means that the active material coating portion accounts for 50% or more, preferably 70% or more, more preferably 90% or more, and particularly preferably 90% or more of the total area of the outer surface of the particle body. means 100% coverage. Note that this ratio (%) (hereinafter sometimes referred to as “coverage”) is the average value for the entire positive electrode active material particles present in the positive electrode active material layer, and this average value is the above lower limit. As far as the above is concerned, it does not exclude the presence of a small amount of positive electrode active material particles that do not have an active material coating portion, that is, that are composed only of particle bodies. When the positive electrode active material particles that do not have the active material coating part are present in the positive electrode active material layer, the amount thereof is preferably 30% by mass with respect to the total amount of the positive electrode active material particles present in the positive electrode active material layer. or less, more preferably 20% by mass or less, and particularly preferably 10% by mass or less.
The coverage can be measured by the following method. First, particles in the positive electrode active material layer are analyzed by energy dispersive X-ray spectroscopy (TEM-EDX) using a transmission electron microscope. Specifically, the outer peripheral portion of the positive electrode active material particles in the TEM image is subjected to elemental analysis by EDX. Elemental analysis is performed on carbon to identify the carbon coating the positive electrode active material particles. A portion where the carbon-covered portion has a thickness of 1 nm or more is defined as a covered portion, and the ratio of the covered portion to the entire circumference of the observed positive electrode active material particle is obtained and used as the coverage ratio. For example, ten positive electrode active material particles are measured, and the average value thereof can be obtained.
In addition, the active material coating part is formed directly on the surface of a particle (hereinafter sometimes referred to as a "core part") composed only of a positive electrode active material and has a thickness of 1 nm to 100 nm, preferably 5 nm to 50 nm. This thickness can be confirmed by TEM-EDX used for the measurement of the coverage rate described above.

活物質被覆部の導電材料は、炭素（導電性炭素）を含む導電性炭素材料であることが好ましい。導電性炭素材料は、炭素のみからなる導電材料でもよく、炭素と炭素以外の他の元素とを含む導電性有機化合物でもよい。他の元素としては、窒素、水素、酸素等が例示できる。前記導電性有機化合物において、他の元素は１０原子％以下が好ましく、５原子％以下がより好ましい。
活物質被覆部を構成する導電材料は、導電性炭素のみからなる導電性炭素材料であることがさらに好ましい。本明細書において「導電性炭素のみからなる」とは、導電性炭素以外の不純物含有量が定量限界以下であることを意味する。
活物質被覆部を有する正極活物質粒子の総質量に対して、活物質被覆部の含有量は０．１～４．０質量％であることが好ましく、０．５～３．０質量％がより好ましく、０．７～２．５質量％がさらに好ましい。
前記活物質被覆部の含有量が高くなると正極活物質層の抵抗値が低減する傾向がある。例えば、正極活物質層の粉体抵抗率が低くなり、急速充放電サイクル容量維持率がより向上しやすい。 The conductive material of the active material coating portion is preferably a conductive carbon material containing carbon (conductive carbon). The conductive carbon material may be a conductive material consisting only of carbon, or a conductive organic compound containing carbon and elements other than carbon. Nitrogen, hydrogen, oxygen and the like can be exemplified as other elements. In the conductive organic compound, the content of other elements is preferably 10 atomic % or less, more preferably 5 atomic % or less.
It is more preferable that the conductive material forming the active material coating portion is a conductive carbon material consisting only of conductive carbon. In the present specification, "consisting only of conductive carbon" means that the content of impurities other than conductive carbon is below the quantitative limit.
The content of the active material coating is preferably 0.1 to 4.0% by mass, more preferably 0.5 to 3.0% by mass, based on the total mass of the positive electrode active material particles having the active material coating. More preferably, 0.7 to 2.5% by mass is even more preferable.
As the content of the active material coating portion increases, the resistance value of the positive electrode active material layer tends to decrease. For example, the powder resistivity of the positive electrode active material layer is lowered, and the rapid charge/discharge cycle capacity retention rate is more likely to be improved.

例えば、活物質被覆部は、予め正極活物質粒子の表面に形成されており、かつ正極活物質層中において、正極活物質粒子の表面に存在する。即ち、本実施形態における活物質被覆部は、正極製造用組成物の調製段階以降の工程で新たに形成されるものではない。加えて、活物質被覆部は、正極製造用組成物の調製段階以降の工程で欠落するものではない。
例えば、正極製造用組成物を調製する際に、被覆粒子を溶媒と共にミキサー等で混合しても、活物質被覆部は正極活物質の表面を被覆している。また、仮に、正極から正極活物質層を剥がし、これを溶媒に投入して正極活物質層中の結着材を溶媒に溶解させた場合にも、活物質被覆部は正極活物質の表面を被覆している。また、仮に、正極活物質層中の粒子の粒度分布をレーザー回折・散乱法により測定する際に、凝集した粒子をほぐす操作を行った場合にも活物質被覆部は正極活物質の表面を被覆している。 For example, the active material coating portion is formed in advance on the surfaces of the positive electrode active material particles, and is present on the surfaces of the positive electrode active material particles in the positive electrode active material layer. That is, the active material coating portion in the present embodiment is not newly formed in the steps after the step of preparing the positive electrode manufacturing composition. In addition, the active material coating portion does not fall off in the steps after the step of preparing the composition for manufacturing a positive electrode.
For example, even when the coated particles are mixed with a solvent in a mixer or the like when preparing the positive electrode-manufacturing composition, the active material-coating portion still covers the surface of the positive electrode active material. Further, even if the positive electrode active material layer is peeled off from the positive electrode and put into a solvent to dissolve the binder in the positive electrode active material layer in the solvent, the active material coating part covers the surface of the positive electrode active material. covered. In addition, even if the particle size distribution of the particles in the positive electrode active material layer is measured by a laser diffraction/scattering method, even if an operation is performed to loosen the aggregated particles, the active material coating portion covers the surface of the positive electrode active material. are doing.

被覆粒子の製造方法としては、例えば、焼結法、蒸着法等が挙げられる。
焼結法としては、正極活物質の粒子と有機物とを含む活物質製造用組成物（例えば、スラリー）を、大気圧下、５００～１０００℃、１～１００時間で焼成する方法が挙げられる。活物質製造用組成物に添加する有機物としては、サリチル酸、カテコール、ヒドロキノン、レゾルシノール、ピロガロール、フロログルシノール、ヘキサヒドロキシベンゼン、安息香酸、フタル酸、テレフタル酸、フェニルアラニン、水分散型フェノール樹脂等、スクロース、グルコース、ラクトース等の糖類、リンゴ酸、クエン酸などのカルボン酸、アリルアルコール、プロパルギルアルコール等の不飽和一価アルコール、アスコルビン酸、ポリビニルアルコール等が挙げられる。この焼結法によれば、活物質製造用組成物を焼成することで、有機物中の炭素を正極活物質の表面に焼結して、活物質被覆部を形成する。
また、他の焼結法としては、いわゆる衝撃焼結被覆法が挙げられる。 Examples of the method for producing coated particles include a sintering method and a vapor deposition method.
Examples of the sintering method include a method of firing a composition (eg, slurry) for producing an active material containing particles of a positive electrode active material and an organic substance under atmospheric pressure at 500 to 1000° C. for 1 to 100 hours. Examples of organic substances added to the active material-producing composition include salicylic acid, catechol, hydroquinone, resorcinol, pyrogallol, phloroglucinol, hexahydroxybenzene, benzoic acid, phthalic acid, terephthalic acid, phenylalanine, water-dispersed phenolic resin, and sucrose. , glucose and lactose, carboxylic acids such as malic acid and citric acid, unsaturated monohydric alcohols such as allyl alcohol and propargyl alcohol, ascorbic acid, and polyvinyl alcohol. According to this sintering method, the active material-producing composition is sintered to sinter carbon in the organic matter onto the surface of the positive electrode active material, thereby forming the active material coating portion.
Another sintering method is the so-called impact sinter coating method.

衝撃焼結被覆法は、例えば、衝撃焼結被覆装置において燃料の炭化水素と酸素の混合ガスを用いてバーナに点火し燃焼室で燃焼させてフレームを発生させ、その際、酸素量を燃料に対して完全燃焼の当量以下にしてフレーム温度を下げ、その後方に粉末供給用ノズルを設置し、そのノズルから被覆する有機物と溶媒を用いて溶かしスラリー状にしたものと燃焼ガスからなる固体―液体―気体三相混合物を粉末供給ノズルから噴射させ、室温に保持された燃焼ガス量を増して、噴射微粉末の温度を下げて、粉末材料の変態温度、昇華温度、蒸発温度以下で加速し、衝撃により瞬時焼結させて、正極活物質の粒子を被覆する。
蒸着法としては、物理気相成長法（ＰＶＤ）、化学気相成長法（ＣＶＤ）等の気相堆積法、メッキ等の液相堆積法等が挙げられる。 In the impact sintering coating method, for example, in an impact sintering coating device, a mixed gas of hydrocarbon and oxygen as a fuel is used to ignite a burner and burn it in a combustion chamber to generate a flame. On the other hand, the flame temperature is lowered to below the equivalent of complete combustion, and a powder supply nozzle is installed behind it, and the solid-liquid consisting of the organic matter to be coated and the solvent melted and made into a slurry from the nozzle and the combustion gas. - Injecting the gaseous three-phase mixture from the powder feed nozzle, increasing the amount of combustion gas maintained at room temperature, lowering the temperature of the injected fine powder, and accelerating it below the transformation temperature, sublimation temperature, and evaporation temperature of the powder material, Instantly sintered by impact to coat the particles of the positive electrode active material.
Vapor deposition methods include vapor deposition methods such as physical vapor deposition (PVD) and chemical vapor deposition (CVD), and liquid phase deposition methods such as plating.

正極活物質粒子の粒子本体は、オリビン型結晶構造を有する化合物を含むことが好ましい。
オリビン型結晶構造を有する化合物は、一般式ＬｉＦｅｘＭ（１－ｘ）ＰＯ４（以下「一般式（Ｉ）」ともいう。）で表される化合物が好ましい。一般式（Ｉ）において０≦ｘ≦１である。ＭはＣｏ、Ｎｉ、Ｍｎ、Ａｌ、Ｔｉ又はＺｒである。物性値に変化がない程度に微小量の、ＦｅおよびＭ（Ｃｏ、Ｎｉ、Ｍｎ、Ａｌ、Ｔｉ又はＺｒ）の一部を他の元素に置換することもできる。一般式（Ｉ）で表される化合物は、微量の金属不純物が含まれていても本発明の効果が損なわれるものではない。 The particle body of the positive electrode active material particles preferably contains a compound having an olivine crystal structure.
The compound having an olivine-type crystal structure is preferably a compound represented by the general formula LiFe x M (1-x) PO 4 (hereinafter also referred to as "general formula (I)"). 0≦x≦1 in general formula (I). M is Co, Ni, Mn, Al, Ti or Zr. A small amount of Fe and M (Co, Ni, Mn, Al, Ti or Zr) can be substituted with other elements to the extent that the physical properties are not changed. Even if the compound represented by the general formula (I) contains a trace amount of metal impurities, the effects of the present invention are not impaired.

一般式（Ｉ）で表される化合物は、ＬｉＦｅＰＯ４で表されるリン酸鉄リチウム（以下、単に「リン酸鉄リチウム」ともいう。）が好ましい。
正極活物質粒子として、リン酸鉄リチウム粒子（粒子本体）の表面の少なくとも一部に導電材料を含む活物質被覆部が存在する被覆リン酸鉄リチウム粒子がより好ましい。電池容量、サイクル特性により優れる点から、リン酸鉄リチウム粒子の表面全体が導電材料で被覆されていることがさらに好ましい。
被覆リン酸鉄リチウム粒子は公知の方法で製造できる。
例えば、特許第５０９８１４６号公報に記載の方法を用いてリン酸鉄リチウム粉末を作製し、ＧＳ Ｙｕａｓａ Ｔｅｃｈｎｉｃａｌ Ｒｅｐｏｒｔ、２００８年６月、第５巻、第１号、第２７～３１頁等に記載の方法を用いて、リン酸鉄リチウム粉末の表面の少なくとも一部を炭素で被覆できる。
具体的には、まず、シュウ酸鉄二水和物、リン酸二水素アンモニウム、及び炭酸リチウムを、特定のモル比で計り、これらを不活性雰囲気下で粉砕及び混合する。次に、得られた混合物を窒素雰囲気下で加熱処理することによってリン酸鉄リチウム粉末を作製する。次いで、リン酸鉄リチウム粉末をロータリーキルンに入れ、窒素をキャリアガスとしたメタノール蒸気を供給しながら加熱処理することによって、表面の少なくとも一部を炭素で被覆したリン酸鉄リチウム粒子を得る。
例えば、粉砕工程における粉砕時間によってリン酸鉄リチウム粒子の粒子径を調整できる。メタノール蒸気を供給しながら加熱処理する工程における加熱時間及び温度等によって、リン酸鉄リチウム粒子を被覆する炭素の量を調整できる。被覆されなかった炭素粒子はその後の分級や洗浄などの工程などにより取り除くことが望ましい。 The compound represented by the general formula (I) is preferably lithium iron phosphate represented by LiFePO 4 (hereinafter also simply referred to as “lithium iron phosphate”).
As the positive electrode active material particles, coated lithium iron phosphate particles having an active material coating portion containing a conductive material on at least part of the surface of the lithium iron phosphate particles (particle main body) are more preferable. From the viewpoint of better battery capacity and cycle characteristics, it is more preferable that the lithium iron phosphate particles are entirely coated with a conductive material.
Coated lithium iron phosphate particles can be produced by known methods.
For example, lithium iron phosphate powder is prepared using the method described in Japanese Patent No. 5098146, and described in GS Yuasa Technical Report, June 2008, Vol. 5, No. 1, pp. 27-31. The method can be used to coat at least a portion of the surface of the lithium iron phosphate powder with carbon.
Specifically, first, iron oxalate dihydrate, ammonium dihydrogen phosphate, and lithium carbonate are weighed in a specific molar ratio, and these are pulverized and mixed under an inert atmosphere. Next, a lithium iron phosphate powder is produced by heat-treating the obtained mixture in a nitrogen atmosphere. Next, the lithium iron phosphate powder is placed in a rotary kiln and heat-treated while supplying methanol vapor using nitrogen as a carrier gas to obtain lithium iron phosphate particles having at least a portion of the surface coated with carbon.
For example, the particle size of the lithium iron phosphate particles can be adjusted by the pulverization time in the pulverization step. The amount of carbon covering the lithium iron phosphate particles can be adjusted by the heating time and temperature in the step of heat-treating while supplying methanol vapor. It is desirable to remove the uncoated carbon particles by subsequent steps such as classification and washing.

正極活物質粒子は、粒子本体が、オリビン型結晶構造を有する化合物以外の他の正極活物質である、他の正極活物質粒子を１種以上含んでもよい。
他の正極活物質は、リチウム遷移金属複合酸化物が好ましい。例えば、コバルト酸リチウム（ＬｉＣｏＯ２）、ニッケル酸リチウム（ＬｉＮｉＯ２）、ニッケルコバルトアルミン酸リチウム（ＬｉＮｉｘＣｏｙＡｌｚＯ２、ただしｘ＋ｙ＋ｚ＝１）、ニッケルコバルトマンガン酸リチウム（ＬｉＮｉｘＣｏｙＭｎｚＯ２、ただしｘ＋ｙ＋ｚ＝１）、マンガン酸リチウム（ＬｉＭｎ２Ｏ４）、コバルトマンガン酸リチウム（ＬｉＭｎＣｏＯ４）、クロム酸マンガンリチウム（ＬｉＭｎＣｒＯ４）、バナジウムニッケル酸リチウム（ＬｉＮｉＶＯ４）、ニッケル置換マンガン酸リチウム（例えば、ＬｉＭｎ１．５Ｎｉ０．５Ｏ４）、及びバナジウムコバルト酸リチウム（ＬｉＣｏＶＯ４）、これらの化合物の一部を金属元素で置換した非化学量論的化合物等が挙げられる。前記金属元素としては、Ｍｎ、Ｍｇ、Ｎｉ、Ｃｏ、Ｃｕ、Ｚｎ及びＧｅからなる群から選択される１種以上が挙げられる。
他の正極活物質粒子は、粒子本体の表面の少なくとも一部に、前記活物質被覆部が存在してもよい。 The positive electrode active material particles may contain one or more other positive electrode active material particles whose particle body is a positive electrode active material other than the compound having an olivine crystal structure.
Another positive electrode active material is preferably a lithium transition metal composite oxide. For example, lithium cobaltate ( LiCoO2 ), lithium nickelate ( LiNiO2 ) , lithium nickel cobalt aluminate ( LiNixCoyAlzO2 , where x + y + z = 1), lithium nickel cobalt manganate ( LiNixCoyMn zO2 , where x+y+z=1), lithium manganate ( LiMn2O4 ), lithium cobalt manganate ( LiMnCoO4 ), lithium manganese chromate ( LiMnCrO4 ) , lithium vanadium nickelate ( LiNiVO4 ), nickel-substituted manganese Lithium oxide (eg, LiMn 1.5 Ni 0.5 O 4 ), lithium vanadium cobaltate (LiCoVO 4 ), non-stoichiometric compounds obtained by substituting a part of these compounds with metal elements, and the like. Examples of the metal element include one or more selected from the group consisting of Mn, Mg, Ni, Co, Cu, Zn and Ge.
Other positive electrode active material particles may have the active material coating portion on at least part of the surface of the particle body.

正極活物質粒子の総質量（活物質被覆部を有する場合は活物質被覆部の質量も含む）に対して、オリビン型結晶構造を有する化合物の含有量は５０質量％以上が好ましく、８０質量％以上がより好ましく、９０質量％以上がさらに好ましい。１００質量％でもよい。
被覆リン酸鉄リチウム粒子を用いる場合、正極活物質粒子の総質量に対して、被覆リン酸鉄リチウム粒子の含有量は５０質量％以上が好ましく、８０質量％以上がより好ましく、９０質量％以上がさらに好ましい。１００質量％でもよい。 The content of the compound having an olivine-type crystal structure is preferably 50% by mass or more, preferably 80% by mass, based on the total mass of the positive electrode active material particles (including the mass of the active material coating portion when the active material coating portion is included). The above is more preferable, and 90% by mass or more is even more preferable. 100 mass % may be sufficient.
When the coated lithium iron phosphate particles are used, the content of the coated lithium iron phosphate particles is preferably 50% by mass or more, more preferably 80% by mass or more, and 90% by mass or more with respect to the total mass of the positive electrode active material particles. is more preferred. 100 mass % may be sufficient.

正極活物質粒子の活物質被覆部の厚さは、１～１００ｎｍが好ましい。
正極活物質粒子の活物質被覆部の厚さは、正極活物質粒子の透過電子顕微鏡（ＴＥＭ）像における活物質被覆部の厚さを計測する方法で測定できる。粒子本体の表面に存在する活物質被覆部の厚さは均一でなくてもよい。粒子本体の表面の少なくとも一部に厚さ１ｎｍ以上の活物質被覆部が存在し、活物質被覆部の厚さの最大値が１００ｎｍ以下であることが好ましい。 The thickness of the active material coating portion of the positive electrode active material particles is preferably 1 to 100 nm.
The thickness of the active material coating portion of the positive electrode active material particles can be measured by measuring the thickness of the active material coating portion in a transmission electron microscope (TEM) image of the positive electrode active material particles. The thickness of the active material coating portion present on the surface of the particle body may not be uniform. It is preferable that an active material-coated portion having a thickness of 1 nm or more exists on at least a part of the surface of the particle body, and the maximum thickness of the active material-coated portion is 100 nm or less.

正極活物質粒子の平均粒子径（活物質被覆部を有する場合は活物質被覆部の厚さも含む）は、例えば０．１～２０．０μｍが好ましく、０．２～１０．０μｍがより好ましい。正極活物質を２種以上用いる場合、それぞれの平均粒子径が上記の範囲内であればよい。
本明細書における正極活物質粒子の平均粒子径は、レーザー回折・散乱法による粒度分布測定器を用いて測定した体積基準のメジアン径である。 The average particle size of the positive electrode active material particles (including the thickness of the active material coating portion if it has an active material coating portion) is, for example, preferably 0.1 to 20.0 μm, more preferably 0.2 to 10.0 μm. When two or more kinds of positive electrode active materials are used, each average particle size should be within the above range.
The average particle size of the positive electrode active material particles in this specification is a volume-based median size measured using a particle size distribution analyzer based on a laser diffraction/scattering method.

［結着材］
正極活物質層１２に含まれる結着材は有機物であり、例えば、ポリアクリル酸、ポリアクリル酸リチウム、ポリフッ化ビニリデン、ポリフッ化ビニリデン－ヘキサフルオロプロピレン共重合体、スチレンブタジエンゴム、ポリビニルアルコール、ポリビニルアセタール、ポリエチレンオキサイド、ポリエチレングリコール、カルボキシメチルセルロース、ポリアクリルニトリル、ポリイミド等が挙げられる。結着材は１種でもよく、２種以上を併用してもよい。
正極活物質層が結着剤を含有する場合、正極活物質層における結着材の含有量は、例えば、正極活物質層の総質量に対して、４．０質量％以下が好ましく、２．０質量％以下がより好ましい。結着材の含有量が上記上限値以下であれば、正極活物質層において、リチウムイオンの伝導に寄与しない物質の割合が少なくなり、電池特性のさらなる向上を図れる。
正極活物質層が結着材を含有する場合、結着材の含有量の下限値は、正極活物質層の総質量に対して０．１質量％以上が好ましく、０．５質量％以上がより好ましい。
即ち、正極活物質層１２が結着材を含有する場合、結着材の含有量は、正極活物質層１２の総質量に対して０．１～１質量％が好ましく、０．１～０．５質量％がより好ましい。 [Binder]
The binder contained in the positive electrode active material layer 12 is an organic substance, and examples thereof include polyacrylic acid, lithium polyacrylate, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, styrene-butadiene rubber, polyvinyl alcohol, and polyvinylidene. Acetal, polyethylene oxide, polyethylene glycol, carboxymethyl cellulose, polyacrylonitrile, polyimide and the like can be mentioned. One type of binder may be used, or two or more types may be used in combination.
When the positive electrode active material layer contains a binder, the content of the binder in the positive electrode active material layer is preferably, for example, 4.0% by mass or less with respect to the total mass of the positive electrode active material layer. 0% by mass or less is more preferable. If the content of the binder is equal to or less than the above upper limit, the ratio of substances that do not contribute to the conduction of lithium ions in the positive electrode active material layer is reduced, and the battery characteristics can be further improved.
When the positive electrode active material layer contains a binder, the lower limit of the content of the binder is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, relative to the total mass of the positive electrode active material layer. more preferred.
That is, when the positive electrode active material layer 12 contains a binder, the content of the binder is preferably 0.1 to 1% by mass, more preferably 0.1 to 0%, based on the total mass of the positive electrode active material layer 12. 0.5% by weight is more preferred.

［導電助剤］
正極活物質層１２に含まれる導電助剤としては、例えば、ケッチェンブラック、アセチレンブラック等のカーボンブラック、グラファイト、グラフェン、ハードカーボン、カーボンナノチューブ（ＣＮＴ）等の導電性炭素材料が挙げられる。導電助剤は１種でもよく、２種以上を併用してもよい。
導電助剤である導電性炭素材料は、炭素のみからなる導電材料でもよく、炭素と炭素以外の他の元素とを含む導電性有機化合物でもよい。他の元素としては、窒素、水素、酸素等が例示できる。前記導電性有機化合物において、他の元素は１０原子％以下が好ましく、５原子％以下がより好ましい。
導電助剤は、導電性炭素のみからなる導電性炭素材料であることがさらに好ましい。本明細書において「導電性炭素のみからなる」とは、導電性炭素以外の不純物含有量が定量限界以下であることを意味する。 [Conductive agent]
Examples of the conductive aid contained in the positive electrode active material layer 12 include carbon black such as ketjen black and acetylene black, conductive carbon materials such as graphite, graphene, hard carbon, and carbon nanotubes (CNT). One type of conductive aid may be used, or two or more types may be used in combination.
The conductive carbon material, which is a conductive aid, may be a conductive material consisting only of carbon, or a conductive organic compound containing carbon and elements other than carbon. Nitrogen, hydrogen, oxygen and the like can be exemplified as other elements. In the conductive organic compound, the content of other elements is preferably 10 atomic % or less, more preferably 5 atomic % or less.
More preferably, the conductive aid is a conductive carbon material consisting only of conductive carbon. In the present specification, "consisting only of conductive carbon" means that the content of impurities other than conductive carbon is below the quantitative limit.

正極活物質層における導電助剤の含有量は、例えば、正極活物質層の総質量に対して、４質量％以下が好ましく、３質量％以下がより好ましく、１質量％以下がさらに好ましく、導電助剤を含まないことが特に好ましく、独立した導電助剤粒子（例えば独立した炭素粒子）が存在しない状態が望ましい。
前記「導電助剤」は、正極活物質とは独立した導電性材料であり、前記独立した導電助剤粒子の他に、繊維状（例えばカーボンナノチューブ）の形状を有する導電性の材料であってもよい。
正極活物質層中において正極活物質粒子に接触している導電助剤は、正極活物質被覆部を構成する導電材料とはみなさない。
正極活物質層に導電助剤を配合する場合、導電助剤の含有量の下限値は、導電助剤の種類に応じて適宜決定され、例えば、正極活物質層の総質量に対して０．１質量％超とされる。
即ち、正極活物質層１２が導電助剤を含有する場合、導電助剤の含有量は、正極活物質層１２の総質量に対して、０．１質量％超１質量％以下が好ましく、０．１質量％超０．５質量％以下がより好ましく、０．１質量％超０．２質量％以下がさらに好ましい。
なお、正極活物質層が「導電助剤を含まない」とは、実質的に含まないことを意味し、本発明の効果に影響を及ぼさない程度に含むものを排除するものではない。例えば、導電助剤の含有量が正極活物質層の総質量に対して０．１質量％以下であれば、実質的に含まれないと判断できる。 The content of the conductive aid in the positive electrode active material layer is, for example, preferably 4% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, relative to the total mass of the positive electrode active material layer. It is particularly preferable not to contain an auxiliary agent, and a state in which independent conductive auxiliary particles (for example, independent carbon particles) are not present is desirable.
The "conductivity aid" is a conductive material independent of the positive electrode active material, and in addition to the independent conductivity aid particles, is a conductive material having a fibrous (e.g., carbon nanotube) shape. good too.
The conductive aid in contact with the positive electrode active material particles in the positive electrode active material layer is not regarded as a conductive material forming the positive electrode active material coating portion.
When the positive electrode active material layer contains the conductive support agent, the lower limit of the content of the conductive support agent is appropriately determined according to the type of the conductive support agent. More than 1% by mass.
That is, when the positive electrode active material layer 12 contains a conductive aid, the content of the conductive aid is preferably more than 0.1% by mass and not more than 1% by mass with respect to the total mass of the positive electrode active material layer 12. 0.5% by mass or less is more preferable, and more than 0.1% by mass and 0.2% by mass or less is more preferable.
In addition, the fact that the positive electrode active material layer "does not contain a conductive aid" means that it does not substantially contain a conductive aid, and does not exclude substances contained to such an extent that the effects of the present invention are not affected. For example, if the content of the conductive aid is 0.1% by mass or less with respect to the total mass of the positive electrode active material layer, it can be determined that it is not substantially contained.

［分散剤］
正極活物質層１２に含まれる分散剤は有機物であり、例えば、ポリビニルピロリドン（ＰＶＰ）、ポリビニルアルコール（ＰＶＡ）、ポリビニルブチラール（ＰＶＢ）、ポリビニルホルマール（ＰＶＦ）等が挙げられる。分散剤は１種でもよく、２種以上を併用してもよい。 [Dispersant]
The dispersant contained in the positive electrode active material layer 12 is an organic substance, and examples thereof include polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinyl formal (PVF), and the like. One dispersant may be used, or two or more dispersants may be used in combination.

［正極集電体本体］
正極集電体本体１４は金属材料からなる。金属材料としては、銅、アルミニウム、チタン、ニッケル、ステンレス鋼等の導電性を有する金属が例示できる。
正極集電体本体１４の厚みは、例えば８～４０μｍが好ましく、１０～２５μｍがより好ましい。
正極集電体本体１４の厚み及び正極集電体１１の厚みは、マイクロメータを用いて測定できる。測定器の一例としてはミツトヨ社製品名「ＭＤＨ－２５Ｍ」が挙げられる。 [Positive electrode current collector body]
The positive electrode current collector main body 14 is made of a metal material. Examples of metal materials include conductive metals such as copper, aluminum, titanium, nickel, and stainless steel.
The thickness of the positive electrode current collector main body 14 is, for example, preferably 8 to 40 μm, more preferably 10 to 25 μm.
The thickness of the positive electrode current collector main body 14 and the thickness of the positive electrode current collector 11 can be measured using a micrometer. An example of the measuring instrument is Mitutoyo's product name "MDH-25M".

［集電体被覆層］
正極集電体本体１４の表面の少なくとも一部に集電体被覆層１５が存在することが好ましい。集電体被覆層１５は導電材料を含む。
ここで、「表面の少なくとも一部」とは、正極集電体本体の表面の面積の１０％～１００％、好ましくは３０％～１００％、より好ましくは５０％～１００％を意味する。
集電体被覆層１５中の導電材料は、炭素（導電性炭素）を含むことが好ましい。炭素のみからなる導電材料がより好ましい。
集電体被覆層１５は、例えばカーボンブラック等の炭素粒子と結着材を含むコーティング層が好ましい。集電体被覆層１５の結着材は、正極活物質層１２の結着材と同様のものを例示できる。
正極集電体本体１４の表面を集電体被覆層１５で被覆した正極集電体１１は、例えば、導電材料、結着材、及び溶媒を含むスラリーを、グラビア法等の公知の塗工方法を用いて正極集電体本体１４の表面に塗工し、乾燥して溶媒を除去する方法で製造できる。 [Current collector coating layer]
It is preferable that the current collector coating layer 15 is present on at least part of the surface of the positive electrode current collector main body 14 . Current collector coating layer 15 includes a conductive material.
Here, "at least part of the surface" means 10% to 100%, preferably 30% to 100%, more preferably 50% to 100% of the surface area of the positive electrode current collector body.
The conductive material in the current collector coating layer 15 preferably contains carbon (conductive carbon). A conductive material consisting only of carbon is more preferable.
The current collector coating layer 15 is preferably a coating layer containing carbon particles such as carbon black and a binder. The binder for the current collector coating layer 15 can be exemplified by the same binder as the binder for the positive electrode active material layer 12 .
The positive electrode current collector 11 in which the surface of the positive electrode current collector main body 14 is coated with the current collector coating layer 15 is coated with a slurry containing a conductive material, a binder, and a solvent by a known coating method such as a gravure method. can be applied to the surface of the positive electrode current collector body 14 using and dried to remove the solvent.

集電体被覆層１５の厚さは、０．１～４．０μｍが好ましい。
集電体被覆層の厚さは、集電体被覆層の断面の透過電子顕微鏡（ＴＥＭ）像又は走査型電子顕微鏡（ＳＥＭ）像における被覆層の厚さを計測する方法で測定できる。集電体被覆層の厚さは均一でなくてもよい。正極集電体本体１４の表面の少なくとも一部に厚さ０．１μｍ以上の集電体被覆層が存在し、集電体被覆層の厚さの最大値が４．０μｍ以下であることが好ましい。 The thickness of the current collector coating layer 15 is preferably 0.1 to 4.0 μm.
The thickness of the current collector coating layer can be measured by measuring the thickness of the coating layer in a transmission electron microscope (TEM) image or a scanning electron microscope (SEM) image of the cross section of the current collector coating layer. The thickness of the current collector coating layer may not be uniform. A current collector coating layer having a thickness of 0.1 μm or more is present on at least a portion of the surface of the positive electrode current collector main body 14, and the maximum thickness of the current collector coating layer is preferably 4.0 μm or less. .

［導電性炭素材料］
本実施形態において、正極活物質層１２は導電性炭素材料を含む。正極活物質層中の導電性炭素材料は、例えば導電助剤、活物質被覆部である。
正極活物質層が導電性炭素材料を含む態様として、下記態様１～３が挙げられる。
態様１：正極活物質層が導電助剤を含まず、正極活物質粒子の粒子本体の表面の少なくとも一部に活物質被覆部が存在し、前記活物質被覆部が導電性炭素材料である態様。
態様２：正極活物質層が導電助剤を含み、かつ正極活物質粒子の粒子本体の表面の少なくとも一部に活物質被覆部が存在し、前記活物質被覆部及び前記導電助剤の一方又は両方が導電性炭素材料である態様。前記活物質被覆部及び前記導電助剤の両方が導電性炭素材料であることが好ましい。
態様３：正極活物質粒子が活物質被覆部を有さず、正極活物質層が導電助剤を含み、導電助剤が導電性炭素材料である態様。
非水電解質二次電池の急速充放電サイクル特性を向上効果に優れる点では、態様１又は２が好ましく、態様１がより好ましい。 [Conductive carbon material]
In this embodiment, the positive electrode active material layer 12 contains a conductive carbon material. The conductive carbon material in the positive electrode active material layer is, for example, a conductive aid and an active material coating.
Examples of embodiments in which the positive electrode active material layer contains a conductive carbon material include the following embodiments 1 to 3.
Aspect 1: Aspect in which the positive electrode active material layer does not contain a conductive aid, an active material coating portion exists on at least a part of the surface of the particle body of the positive electrode active material particles, and the active material coating portion is a conductive carbon material. .
Aspect 2: The positive electrode active material layer contains a conductive aid, and an active material coating portion exists on at least part of the surface of the particle body of the positive electrode active material particles, and one of the active material coating portion and the conductive aid, or Embodiments in which both are conductive carbon materials. Both the active material coating portion and the conductive aid are preferably conductive carbon materials.
Aspect 3: An aspect in which the positive electrode active material particles do not have an active material coating portion, the positive electrode active material layer contains a conductive aid, and the conductive aid is a conductive carbon material.
Aspect 1 or 2 is preferable, and aspect 1 is more preferable, from the viewpoint of improving the rapid charge-discharge cycle characteristics of the non-aqueous electrolyte secondary battery.

［低抵抗導電性炭素材料の含有量］
本実施形態における正極活物質層は、正極活物質層中に存在する導電性炭素材料のうち、低抵抗であるものが少ない。
具体的に、正極活物質層の総質量に対して、抵抗率が０．１０Ω・ｃｍ以下である低抵抗導電性炭素材料（以下、「低抵抗導電性炭素材料（Ｃ１）」ともいう。）の含有量は０．５質量％以下であり、０．３質量％以下が好ましく、０．２質量％以下がより好ましく、０．１質量％以下がさらに好ましい。ゼロでもよい。
低抵抗導電性炭素材料（Ｃ１）の含有量が上記上限値以下であると、急速充放電サイクル特性の向上効果に優れる。 [Content of low resistance conductive carbon material]
In the positive electrode active material layer of the present embodiment, few of the conductive carbon materials present in the positive electrode active material layer have low resistance.
Specifically, a low-resistance conductive carbon material (hereinafter also referred to as “low-resistance conductive carbon material (C1)”) having a resistivity of 0.10 Ω·cm or less with respect to the total mass of the positive electrode active material layer. is 0.5% by mass or less, preferably 0.3% by mass or less, more preferably 0.2% by mass or less, and even more preferably 0.1% by mass or less. May be zero.
When the content of the low-resistance conductive carbon material (C1) is equal to or less than the above upper limit, the effect of improving rapid charge-discharge cycle characteristics is excellent.

また、正極活物質層の総質量に対して、抵抗率が０．０２Ω・ｃｍ以下である低抵抗導電性炭素材料（以下、「低抵抗導電性炭素材料（Ｃ２）」ともいう。）の含有量が０．５質量％以下であることが好ましく、０．３質量％以下がより好ましく、０．２質量％以下がさらに好ましく、０．１質量％以下が特に好ましい。ゼロでもよい。ここで、前記低抵抗導電性炭素材料（Ｃ２）の含有量が、上記所定値以下であれば、前記低抵抗導電性炭素材料（Ｃ１）の含有量が上記所定値を超える場合（例えば０．５質量超である場合）であっても本発明の態様に含まれる。即ち、本発明においては、低抵抗導電性炭素材料（Ｃ１）及び／又は低抵抗導電性炭素材料（Ｃ２）の含有量が０．５質量％以下であることが好ましく、０．３質量％以下がより好ましく、０．２質量％以下がさらに好ましく、０．１質量％以下が特に好ましい。ゼロでもよい。
低抵抗導電性炭素材料（Ｃ２）の含有量が上記上限値以下であると、急速充放電サイクル特性の向上効果により優れる。 In addition, a low-resistance conductive carbon material having a resistivity of 0.02 Ω·cm or less (hereinafter also referred to as “low-resistance conductive carbon material (C2)”) is contained with respect to the total mass of the positive electrode active material layer. The amount is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, even more preferably 0.2% by mass or less, and particularly preferably 0.1% by mass or less. May be zero. Here, when the content of the low-resistance conductive carbon material (C2) is equal to or less than the predetermined value, when the content of the low-resistance conductive carbon material (C1) exceeds the predetermined value (for example, 0.5%). more than 5 mass) is included in the aspect of the present invention. That is, in the present invention, the content of the low-resistance conductive carbon material (C1) and/or the low-resistance conductive carbon material (C2) is preferably 0.5% by mass or less, and 0.3% by mass or less. is more preferable, 0.2% by mass or less is more preferable, and 0.1% by mass or less is particularly preferable. May be zero.
When the content of the low-resistance conductive carbon material (C2) is equal to or less than the above upper limit, the effect of improving rapid charge-discharge cycle characteristics is excellent.

正極活物質層における低抵抗導電性炭素材料（Ｃ１）又は（Ｃ２）の含有量は、正極活物質層中に独立して存在する導電性炭素粒子の量を少なくすることによって低減できる。例えば、抵抗率が０．１０Ω・ｃｍ以下である導電助剤の配合量をゼロ又は極力低減することで、低抵抗導電性炭素材料（Ｃ１）の含有量を低減できる。また、抵抗率が０．０２Ω・ｃｍ以下である導電助剤の配合量をゼロ又は極力低減することで、低抵抗導電性炭素材料（Ｃ２）の含有量を低減できる。
導電助剤の抵抗率は、後述の≪導電助剤の抵抗率Ｒ４の測定方法≫により測定できる。 The content of the low-resistance conductive carbon material (C1) or (C2) in the positive electrode active material layer can be reduced by reducing the amount of conductive carbon particles independently present in the positive electrode active material layer. For example, the content of the low-resistance conductive carbon material (C1) can be reduced by reducing the blending amount of the conductive additive having a resistivity of 0.10 Ω·cm or less to zero or as much as possible. In addition, the content of the low-resistance conductive carbon material (C2) can be reduced by reducing the content of the conductive additive having a resistivity of 0.02 Ω·cm or less to zero or as much as possible.
The resistivity of the conductive aid can be measured by <<Method for measuring resistivity R4 of conductive aid>> described below.

［活物質被覆部の抵抗率及び含有量］
正極活物質層１２は、導電性炭素材料である活物質被覆部を含むことが好ましい。活物質被覆部の抵抗率は０．１５Ω・ｃｍ以上が好ましく、０．２０Ω・ｃｍ以上が好ましく、０．２５Ω・ｃｍ以上がさらに好ましい。活物質被覆部の抵抗率が上記下限値以上であると、良好な急速充放電サイクル容量維持率が得られやすい。
活物質被覆部の抵抗率の上限は、正極活物質層の抵抗値が高くなりすぎない点で、１．０Ω・ｃｍ以下が好ましく、０．５Ω・ｃｍ以下がより好ましく、０．４Ω・ｃｍ以下がさらに好ましい。
即ち、活物質被覆部の抵抗率は０．１５Ω・ｃｍ～１．０Ω・ｃｍが好ましく、０．２０Ω・ｃｍ～０．５Ω・ｃｍがより好ましく、０．２５Ω・ｃｍ～０．４Ω・ｃｍがさらに好ましい。
活物質被覆部の抵抗率は、粒子本体の表面に炭素材料を被覆する際の製造条件を変えることによって調整できる。
活物質被覆部の抵抗率は、後述の≪活物質被覆部の抵抗率Ｒ２の測定方法≫により測定できる。 [Resistivity and Content of Active Material Coating Portion]
The positive electrode active material layer 12 preferably includes an active material coating portion made of a conductive carbon material. The resistivity of the active material coating portion is preferably 0.15 Ω·cm or more, preferably 0.20 Ω·cm or more, and more preferably 0.25 Ω·cm or more. When the resistivity of the active material-coated portion is equal to or higher than the above lower limit, it is easy to obtain a good rapid charge/discharge cycle capacity retention rate.
The upper limit of the resistivity of the active material coating portion is preferably 1.0 Ω·cm or less, more preferably 0.5 Ω·cm or less, and 0.4 Ω·cm in order to prevent the resistance value of the positive electrode active material layer from becoming too high. More preferred are:
That is, the resistivity of the active material coating portion is preferably 0.15 Ω·cm to 1.0 Ω·cm, more preferably 0.20 Ω·cm to 0.5 Ω·cm, and more preferably 0.25 Ω·cm to 0.4 Ω·cm. is more preferred.
The resistivity of the active material-coated portion can be adjusted by changing the manufacturing conditions when the surface of the particle body is coated with the carbon material.
The resistivity of the active material-coated portion can be measured by <<Method for measuring resistivity R2 of the active material-coated portion>> described later.

正極活物質層の総質量に対して、活物質被覆部の含有量は０．９質量％以上が好ましく、１．０質量％以上がより好ましく、１．１質量％以上がさらに好ましい。活物質被覆部の含有量の上限は、正極活物質層の総質量に対する導電性炭素含有量が、後述する好ましい範囲を越えない値であることが好ましい。
前記活物質被覆部の含有量が上記範囲の下限値以上であると正極活物質層の抵抗値の低減効果に優れ、上限値以下であると電池としてのエネルギー密度が高くなりやすい。
正極活物質層の総質量に対する活物質被覆部の含有量は、正極活物質粒子に対する活物質被覆部（導電性炭素材料）の含有割合と、正極活物質粒子の配合量によって調整できる。 The content of the active material covering portion is preferably 0.9% by mass or more, more preferably 1.0% by mass or more, and even more preferably 1.1% by mass or more, relative to the total mass of the positive electrode active material layer. The upper limit of the content of the active material coating portion is preferably a value such that the content of conductive carbon relative to the total mass of the positive electrode active material layer does not exceed the preferred range described below.
When the content of the active material coating portion is at least the lower limit of the above range, the effect of reducing the resistance value of the positive electrode active material layer is excellent, and when it is at most the upper limit, the energy density of the battery tends to increase.
The content of the active material coating portion with respect to the total mass of the positive electrode active material layer can be adjusted by the content ratio of the active material coating portion (conductive carbon material) to the positive electrode active material particles and the compounding amount of the positive electrode active material particles.

［導電性炭素含有量］
正極活物質層の総質量に対して、導電性炭素の含有量は０．９～４．０質量％が好ましく、１．０～３．０質量％がより好ましく、１．１～２．５質量％がさらに好ましい。
正極活物質層中の導電性炭素の含有量が上記範囲の下限値以上であると正極活物質層の抵抗値の低減効果に優れ、上限値以下であると電池としてのエネルギー密度が高くなりやすい。
活物質被覆部及び導電助剤が、導電性炭素のみからなる導電性炭素材料である場合、正極活物質層の総質量に対する導電性炭素の含有量は、正極活物質層の総質量に対する活物質被覆部の含有量及び導電材料の含有量の合計である。 [Conductive carbon content]
The content of conductive carbon is preferably 0.9 to 4.0% by mass, more preferably 1.0 to 3.0% by mass, and 1.1 to 2.5% by mass relative to the total mass of the positive electrode active material layer. % by mass is more preferred.
When the content of conductive carbon in the positive electrode active material layer is at least the lower limit of the above range, the effect of reducing the resistance value of the positive electrode active material layer is excellent, and when it is at most the upper limit, the energy density of the battery tends to increase. .
When the active material coating portion and the conductive aid are a conductive carbon material consisting only of conductive carbon, the content of the conductive carbon with respect to the total mass of the positive electrode active material layer is the active material with respect to the total mass of the positive electrode active material layer. It is the sum of the content of the covering portion and the content of the conductive material.

正極活物質層の総質量に対する導電性炭素の含有量は、正極集電体上の正極活物質層をスパチュラ等で削り採った粉体（粒子群）を測定対象粉体として後述の≪導電性炭素含有量の測定方法≫で測定できる。
後述の≪導電性炭素含有量の測定方法≫で測定した導電性炭素の含有量は、活物質被覆部中の炭素と、導電助剤中の炭素を含む。結着材中の炭素は含まれない。分散剤中の炭素は含まれない。 The content of conductive carbon with respect to the total mass of the positive electrode active material layer is measured by using a powder (particle group) obtained by scraping the positive electrode active material layer on the positive electrode current collector with a spatula or the like as the powder to be measured. Measurement method of carbon content>>.
The content of conductive carbon measured by <<Method for Measuring Content of Conductive Carbon>> described below includes carbon in the active material coating portion and carbon in the conductive aid. Carbon in the binder is not included. Carbon in the dispersant is not included.

なお、正極集電体上の正極活物質層を削り採った粉体を測定対象粉体とする場合は、正極活物質層を構成する粉体のみを得るために、正極集電体と正極活物質層との界面から５μｍ以上離れた部分の正極活物質層を削り採る。すなわち、正極集電体本体上に集電体被覆層が存在する場合、集電体被覆層は削り採らない。削り採った粉体を１２０℃、４時間の条件で真空乾燥したものを測定対象粉体とする。以下の測定方法において、特に断りがない限り同様である。 In addition, when the powder obtained by scraping off the positive electrode active material layer on the positive electrode current collector is used as the powder to be measured, the positive electrode current collector and the positive electrode active material are separated from each other in order to obtain only the powder constituting the positive electrode active material layer. A portion of the positive electrode active material layer at a distance of 5 μm or more from the interface with the material layer is scraped off. That is, when the current collector coating layer exists on the positive electrode current collector main body, the current collector coating layer is not scraped off. The scraped powder is vacuum-dried at 120° C. for 4 hours and used as the powder to be measured. Unless otherwise specified, the same applies to the following measurement methods.

［正極活物質層の粉体抵抗率］
正極活物質層１２の粉体抵抗率は１０～１，０００Ω・ｃｍが好ましく、１１～１００Ω・ｃｍが好ましく、１２～５０Ω・ｃｍがより好ましい。
正極活物質層の粉体抵抗率は、正極集電体上の正極活物質層をスパチュラ等で削り採った粉体（粒子群）を測定対象粉体として、後述の＜粉体抵抗率Ｒ１の測定方法＞で測定できる。測定ばらつきの影響を避けるため、加圧成形した成形サンプルの質量密度が２．０～２．４ｇ／ｃｍ３の範囲となるように、加圧力を設定することが好ましい。
正極活物質層の粉体抵抗率が上記範囲の下限値以上であると高いサイクル容量維持率が得られ、上限値以下であると急速な充放電特性が得られる。
前記粉体抵抗率は、例えば、正極活物質の種類、活物質被覆の含有量、導電助剤の含有量等によって調整できる。活物質被覆の含有量が多いと粉体抵抗率は低くなる傾向がある。また導電助剤の含有量が少ないと粉体抵抗率は高くなる傾向がある。 [Powder resistivity of positive electrode active material layer]
The powder resistivity of the positive electrode active material layer 12 is preferably 10 to 1,000 Ω·cm, preferably 11 to 100 Ω·cm, more preferably 12 to 50 Ω·cm.
The powder resistivity of the positive electrode active material layer is measured using powder (particle group) obtained by scraping the positive electrode active material layer on the positive electrode current collector with a spatula or the like as the powder to be measured . measurement method>. In order to avoid the influence of measurement variations, it is preferable to set the pressure so that the mass density of the pressure-molded molded sample is in the range of 2.0 to 2.4 g/cm 3 .
When the powder resistivity of the positive electrode active material layer is at least the lower limit of the above range, a high cycle capacity retention rate can be obtained, and when it is at most the upper limit, rapid charge-discharge characteristics can be obtained.
The powder resistivity can be adjusted by, for example, the type of positive electrode active material, the content of the active material coating, the content of the conductive aid, and the like. The higher the active material coating content, the lower the powder resistivity. Also, when the content of the conductive aid is small, the powder resistivity tends to be high.

≪活物質被覆部の抵抗率Ｒ２の測定方法≫
正極活物質からなる粒子本体の表面に活物質被覆部を有する正極活物質粒子において、導電性炭素材料（活物質被覆部）に比べて抵抗率が大幅に高い正極活物質（例えば、リン酸鉄リチウム）は絶縁体とみなすことができる。
導電性炭素材料と絶縁体とからなる測定対象粉体における導電性炭素材料の抵抗率Ｒ２（単位：Ω・ｃｍ）は、下記式（１）により求めることができる。
Ｒ２＝Ｒ１×Ｑ１×ρ１／ρ２ （１）
式（１）において、Ｒ１は測定対象粉体の粉体抵抗率（単位：Ω・ｃｍ）である。下記＜粉体抵抗率Ｒ１の測定方法＞で測定できる。
Ｑ１（単位：体積％）は測定対象粉体の総体積に対する導電性炭素材料の体積比率（単位：体積％）である。下記＜体積比率Ｑ１の求め方＞で求めることができる。
ρ１（単位：ｇ／ｃｍ３）は測定対象粉体の質量密度である。＜粉体抵抗率Ｒ１の測定方法＞において、測定対象粉体を加圧成形した成形サンプルの質量と外形寸法から求める。
ρ２（単位：ｇ／ｃｍ３）は測定対象粉体の真密度である。乾式自動密度計（Ｈｅを使用）により測定できる。 <<Method for measuring resistivity R2 of active material coating portion>>
In a positive electrode active material particle having an active material coating on the surface of a particle body made of a positive electrode active material, a positive electrode active material (e.g., iron phosphate) having a significantly higher resistivity than a conductive carbon material (active material coating) Lithium) can be considered an insulator.
The resistivity R 2 (unit: Ω·cm) of the conductive carbon material in the measurement object powder composed of the conductive carbon material and the insulator can be obtained by the following formula (1).
R2 = R1 *Q1 * [rho] 1 /[rho] 2 (1)
In formula (1), R1 is the powder resistivity (unit: Ω·cm) of the powder to be measured. It can be measured by the following <Method for measuring powder resistivity R1 >.
Q 1 (unit: volume %) is the volume ratio (unit: volume %) of the conductive carbon material to the total volume of the powder to be measured. It can be obtained by <How to obtain the volume ratio Q1 > below.
ρ 1 (unit: g/cm 3 ) is the mass density of the powder to be measured. In <Measuring method of powder resistivity R1 >, it is obtained from the mass and external dimensions of a compacted sample obtained by pressure-molding the powder to be measured.
ρ 2 (unit: g/cm 3 ) is the true density of the powder to be measured. It can be measured by a dry automatic density meter (using He).

＜粉体抵抗率Ｒ１の測定方法＞
粉体抵抗測定装置を用いて測定対象粉体の粉体抵抗率Ｒ１を測定する。
粉体抵抗測定では、測定対象粉体を測定セルに投入し、加圧成形した際の粉体抵抗率（単位：Ω・ｃｍ）及び成形サンプルの厚みを測定する。加圧力は測定対象物によって適宜設定できる。
また成形サンプルの質量と厚みの値から測定時の質量密度ρ１（単位：ｇ／ｃｍ３）を求める。 <Method for measuring powder resistivity R1 >
The powder resistivity R1 of the powder to be measured is measured using a powder resistance measuring device.
In the powder resistance measurement, the powder to be measured is put into a measurement cell, and the powder resistivity (unit: Ω·cm) and the thickness of the molded sample are measured when pressure-molded. The applied pressure can be appropriately set depending on the object to be measured.
Also, the mass density ρ 1 (unit: g/cm 3 ) at the time of measurement is obtained from the mass and thickness values of the molded sample.

＜体積比率Ｑ１の求め方＞
下記式（２）により体積比率Ｑ１（単位：体積％）を求める。
Ｑ１＝（ｍ１／ρ４）／{（１－ｍ１）／ρ３＋ｍ１／ρ４} （２）
式（２）において、ｍ１（単位：質量％）は、測定対象粉体中の導電性炭素材料（活物質被覆部）の含有量である。導電性炭素のみからなる導電性炭素材料（活物質被覆部）の含有量は、後述の≪導電性炭素含有量の測定方法≫の測定方法Ａ～Ｃのいずれかの方法で測定できる。
ρ３（単位：ｇ／ｃｍ３）は、測定対象粉体中の絶縁体（正極活物質）の真密度である。例えば、リン酸鉄リチウムの理論値は３．６である。
ρ４（単位：ｇ／ｃｍ３）は、測定対象粉体中の導電性炭素材料（活物質被覆部）の真密度である。例えば、非晶質炭素の理論値は２．０である。 <How to find the volume ratio Q1 >
A volume ratio Q 1 (unit: volume %) is obtained by the following formula (2).
Q 1 = (m 1 /ρ 4 )/{(1−m 1 )/ρ 3 +m 1 /ρ 4 } (2)
In formula (2), m 1 (unit: mass %) is the content of the conductive carbon material (active material coating portion) in the powder to be measured. The content of the conductive carbon material (active material coating portion) composed only of conductive carbon can be measured by any one of the measurement methods A to C of <<Method for measuring conductive carbon content>> described below.
ρ 3 (unit: g/cm 3 ) is the true density of the insulator (positive electrode active material) in the powder to be measured. For example, the theoretical value for lithium iron phosphate is 3.6.
ρ 4 (unit: g/cm 3 ) is the true density of the conductive carbon material (active material coating portion) in the powder to be measured. For example, the theoretical value for amorphous carbon is 2.0.

このようにして、正極活物質粒子（原料）を測定対象粉体とし、上記式（１）により、活物質被覆部の抵抗率Ｒ２を測定できる。なお、正極活物質の電導度が高い場合は、正極活物質の抵抗率を勘案して活物質被覆部の抵抗率Ｒ２を求めることができる。 In this manner, the positive electrode active material particles (raw material) are used as powders to be measured, and the resistivity R2 of the active material coating portion can be measured by the above formula (1). Note that when the positive electrode active material has a high electrical conductivity, the resistivity R2 of the active material covering portion can be obtained in consideration of the resistivity of the positive electrode active material.

また、正極活物質層に導電助剤が実質的に含まれない場合、正極集電体上の正極活物質層を削り採った粉体を測定対象粉体として、上記式（１）により、活物質被覆部の抵抗率Ｒ２を測定できる。測定対象粉体において、導電性炭素材料に比べて抵抗率が大幅に高い正極活物質及び結着材（例えばポリフッ化ビニリデン）は絶縁体とみなすことができる。 正極活物質層における導電助剤の有無は、後述の≪導電性炭素の分析方法≫で判別できる。 In addition, when the positive electrode active material layer does not substantially contain the conductive aid, the powder obtained by scraping off the positive electrode active material layer on the positive electrode current collector is used as the powder to be measured, and the active material is calculated according to the above formula (1). The resistivity R2 of the material coating can be measured. In the powder to be measured, the positive electrode active material and binder (for example, polyvinylidene fluoride), which have significantly higher resistivity than the conductive carbon material, can be regarded as insulators. The presence or absence of the conductive aid in the positive electrode active material layer can be determined by the <<analytical method of conductive carbon>> described below.

≪導電助剤の抵抗率Ｒ４の測定方法≫
導電性炭素材料である導電助剤の抵抗率Ｒ４（単位：Ω・ｃｍ）は、下記式（３）により求めることができる。
Ｒ４＝Ｒ３×ρ５／ρ６ （３）
式（３）において、Ｒ３は導電助剤の粉体抵抗率（単位：Ω・ｃｍ）である。Ｒ３は、導電助剤（原料）を測定対象粉体として、上記＜粉体抵抗率Ｒ３の測定方法＞で測定できる。
ρ５（単位：ｇ／ｃｍ３）は導電助剤の質量密度である。＜粉体抵抗率Ｒ１の測定方法＞において、測定対象粉体を加圧成形した成形サンプルの質量と外形寸法から求める。
ρ６（単位：ｇ／ｃｍ３）は導電助剤の真密度である。乾式自動密度計（Ｈｅを使用）により測定できる。
なお、導電助剤を測定対象粉体として粉体抵抗率Ｒ３を測定する場合、測定ばらつきの影響を避けるため、加圧成形した成形サンプルの質量密度が０．６～０．８ｇ／ｃｍ３の範囲となるように、加圧力を設定することが好ましい。 <<Method for measuring resistivity R4 of conductive aid>>
The resistivity R 4 (unit: Ω·cm) of the conductive aid, which is a conductive carbon material, can be obtained by the following formula (3).
R 4 =R 3 ×ρ 5 /ρ 6 (3)
In formula (3), R3 is the powder resistivity (unit: Ω·cm) of the conductive aid. R 3 can be measured by the above <Measuring method of powder resistivity R 3 > using the conductive additive (raw material) as the powder to be measured.
ρ 5 (unit: g/cm 3 ) is the mass density of the conductive aid. In <Measuring method of powder resistivity R1 >, it is obtained from the mass and external dimensions of a compacted sample obtained by pressure-molding the powder to be measured.
ρ 6 (unit: g/cm 3 ) is the true density of the conductive aid. It can be measured by a dry automatic density meter (using He).
In addition, when measuring the powder resistivity R 3 with the conductive additive as the powder to be measured, the mass density of the pressure-molded sample is 0.6 to 0.8 g / cm 3 in order to avoid the influence of measurement variation. It is preferable to set the applied pressure so as to fall within the range of

このようにして、導電助剤（原料）を測定対象粉体とし、上記式（３）により、導電助剤の抵抗率Ｒ４を測定できる。
また、正極活物質層の拡がり抵抗値分布を用いて、正極活物質層中に存在する導電助剤の種類を同定し、同定した導電助剤（原料）を測定対象粉体とすることにより、正極活物質層中の導電助剤の抵抗率Ｒ４を求めることができる。
例えば、後述の＜拡がり抵抗値分布の測定方法＞で正極活物質層の拡がり抵抗値分布を測定すると、正極活物質層中に導電助剤が存在する場合は、拡がり抵抗値が６（単位：ｌｏｇΩ）以下の領域にピークが現れる。既知の導電助剤をバインダーで包埋した同定用サンプルを測定対象とし、同様に拡がり抵抗値分布を測定して同定する。 In this way, the conductive additive (raw material) is used as the powder to be measured, and the resistivity R4 of the conductive additive can be measured according to the above formula (3).
Further, by using the spreading resistance value distribution of the positive electrode active material layer to identify the type of conductive aid present in the positive electrode active material layer, and using the identified conductive aid (raw material) as the powder to be measured, It is possible to obtain the resistivity R4 of the conductive aid in the positive electrode active material layer.
For example, when the spreading resistance value distribution of the positive electrode active material layer is measured by <Method for Measuring Spreading Resistance Value Distribution> described later, the spreading resistance value is 6 (unit: logΩ) peak appears in the region below. An identification sample in which a known conductive agent is embedded in a binder is used as a measurement object, and the spreading resistance value distribution is similarly measured and identified.

≪導電助剤の含有量の測定方法≫
後述の＜拡がり抵抗値分布の測定方法＞で測定した正極活物質層の拡がり抵抗値分布において、全体のピーク面積に対する、導電助剤のピーク面積の割合を求める。
具体的には、拡がり抵抗値４．０～１２．５（ｌｏｇΩ）の頻度合計を１００％とするとき、拡がり抵抗値４．０～６．０（ｌｏｇΩ）の頻度合計の割合を求める。
この割合を正極活物質層に対する導電助剤の体積割合α１（単位：体積％）とみなし、下記式（４）により正極活物質層の総質量に対する導電助剤の含有量α２（単位：質量％）求めることができる。
α２＝α１×ρ５／ρ６ （４）
式（４）において、ρ５、ρ６は前記式（３）におけるρ５、ρ６と同じである。 <<Method for measuring the content of the conductive aid>>
In the spreading resistance value distribution of the positive electrode active material layer measured by <Method for Measuring Spreading Resistance Value Distribution> described later, the ratio of the peak area of the conductive aid to the total peak area is obtained.
Specifically, when the total frequency of spreading resistance values of 4.0 to 12.5 (log Ω) is taken as 100%, the ratio of the total frequency of spreading resistance values of 4.0 to 6.0 (log Ω) is obtained.
This ratio is regarded as the volume ratio α1 (unit: volume %) of the conductive aid with respect to the positive electrode active material layer, and the content α2 (unit: mass%) of the conductive aid with respect to the total mass of the positive electrode active material layer is calculated by the following formula (4). ) can be requested.
α2=α1× ρ5 / ρ6 (4)
In Equation (4), ρ 5 and ρ 6 are the same as ρ 5 and ρ 6 in Equation (3) above.

＜拡がり抵抗値分布の測定方法＞
拡がり抵抗値分布は、走査型拡がり抵抗顕微鏡（ＳＳＲＭ：Ｓｃａｎｎｉｎｇ Ｓｐｒｅａｄ Ｒｅｓｉｓｔａｎｃｅ Ｍｉｃｒｏｓｃｏｐｅ）を用いて測定できる。
ＳＳＲＭは、測定対象物にバイアス電圧を印加し、表面を導電性探針で走査し、探針直下の抵抗値（拡がり抵抗値）の分布を二次元的に計測する。
拡がり抵抗値分布の測定は、ＳＳＲＭを用い、ＤＣバイアス電圧＋２．０Ｖ、スキャンサイズ６０μｍ×６０μｍ、測定点の数（データ点数）１０２４×１０２４の条件で行い、横軸を拡がり抵抗値、縦軸を頻度とする度数分布のグラフ（拡がり抵抗値分布）を得る。
縦軸の頻度は、抵抗値が４．０ｌｏｇΩ（１×１０４Ω）以上、１２．５ｌｏｇΩ（１×１０１２．５Ω）以下である頻度（測定点の数）の合計を１００％とするときの相対頻度（単位：％、単に「頻度」ともいう）とする。 <Method for measuring spreading resistance value distribution>
The spreading resistance value distribution can be measured using a scanning spreading resistance microscope (SSRM).
The SSRM applies a bias voltage to an object to be measured, scans the surface with a conductive probe, and two-dimensionally measures the distribution of resistance values (spreading resistance values) immediately below the probe.
The spreading resistance value distribution was measured using an SSRM under the conditions of a DC bias voltage of +2.0 V, a scan size of 60 μm×60 μm, and the number of measurement points (number of data points) of 1024×1024. A frequency distribution graph (spreading resistance value distribution) is obtained.
The frequency on the vertical axis is the total frequency (number of measurement points) at which the resistance value is 4.0 log Ω (1 × 10 4 Ω) or more and 12.5 log Ω (1 × 10 12.5 Ω) or less. relative frequency (unit: %, also simply referred to as “frequency”).

≪導電性炭素含有量の測定方法≫
［測定方法Ａ］
測定対象物を均一に混合して試料（質量ｗ１）を量りとり、下記の工程Ａ１、工程Ａ２の手順で熱重量示差熱（ＴＧ－ＤＴＡ）測定を行い、ＴＧ曲線を得る。得られたＴＧ曲線から下記第１の重量減少量Ｍ１（単位：質量％）及び第２の重量減少量Ｍ２（単位：質量％）を求める。Ｍ２からＭ１を減算して導電性炭素の含有量（単位：質量％）を得る。
工程Ａ１：３００ｍＬ／分のアルゴン気流中において、１０℃／分の昇温速度で３０℃から６００℃まで昇温し、６００℃で１０分間保持したときの質量ｗ２から、下記式（ａ１）により第１の重量減少量Ｍ１を求める。
Ｍ１＝（ｗ１－ｗ２）／ｗ１×１００ …（ａ１）
工程Ａ２：前記工程Ａ１の直後に６００℃から１０℃／分の降温速度で降温し、２００℃で１０分間保持した後に、測定ガスをアルゴンから酸素へ完全に置換し、１００ｍＬ／分の酸素気流中において、１０℃／分の昇温速度で２００℃から１０００℃まで昇温し、１０００℃にて１０分間保持したときの質量ｗ３から、下記式（ａ２）により第２の重量減少量Ｍ２（単位：質量％）を求める。
Ｍ２＝（ｗ１－ｗ３）／ｗ１×１００ …（ａ２） <<Method for measuring conductive carbon content>>
[Measurement method A]
The object to be measured is uniformly mixed, a sample (mass w1) is weighed, thermogravimetric differential thermal analysis (TG-DTA) is performed in the following steps A1 and A2, and a TG curve is obtained. From the obtained TG curve, the following first weight reduction amount M1 (unit: mass %) and second weight reduction amount M2 (unit: mass %) are determined. Subtract M1 from M2 to obtain the content of conductive carbon (unit: % by mass).
Step A1: In an argon stream of 300 mL/min, the temperature is raised from 30 ° C. to 600 ° C. at a temperature increase rate of 10 ° C./min, and the mass w2 when held at 600 ° C. for 10 minutes is calculated by the following formula (a1) A first weight reduction amount M1 is obtained.
M1=(w1-w2)/w1×100 (a1)
Step A2: Immediately after Step A1, the temperature is lowered from 600° C. at a temperature drop rate of 10° C./min, held at 200° C. for 10 minutes, and then the measurement gas is completely replaced from argon to oxygen with an oxygen flow of 100 mL/min. Inside, the temperature is increased from 200 ° C. to 1000 ° C. at a temperature increase rate of 10 ° C./min, and the mass w3 when held at 1000 ° C. for 10 minutes is calculated by the following formula (a2) to obtain the second weight reduction amount M2 ( Unit: % by mass).
M2=(w1-w3)/w1×100 (a2)

［測定方法Ｂ］
測定対象物を均一に混合して試料を０．０００１ｍｇ精秤し、下記の燃焼条件で試料を燃焼し、発生した二酸化炭素をＣＨＮ元素分析装置により定量し、試料に含まれる全炭素量Ｍ３（単位：質量％）を測定する。また、前記測定方法Ａの工程Ａ１の手順で第１の重量減少量Ｍ１を求める。Ｍ３からＭ１を減算して導電性炭素の含有量（単位：質量％）を得る。
［燃焼条件］
燃焼炉：１１５０℃
還元炉：８５０℃
ヘリウム流量：２００ｍＬ／分
酸素流量：２５～３０ｍＬ／分 [Measurement method B]
The object to be measured is uniformly mixed and 0.0001 mg of the sample is accurately weighed, the sample is burned under the following combustion conditions, the carbon dioxide generated is quantified by a CHN elemental analyzer, and the total carbon content M3 ( Unit: % by mass). In addition, the first weight reduction amount M1 is obtained by the procedure of step A1 of the measuring method A described above. Subtract M1 from M3 to obtain the conductive carbon content (unit: % by mass).
[Combustion conditions]
Combustion furnace: 1150°C
Reduction furnace: 850°C
Helium flow rate: 200 mL/min Oxygen flow rate: 25-30 mL/min

［測定方法Ｃ］
上記測定方法Ｂと同様にして、試料に含まれる全炭素量Ｍ３（単位：質量％）を測定する。また、下記の方法で結着材由来の炭素の含有量Ｍ４（単位：質量％）を求める。Ｍ３からＭ４を減算して導電性炭素の含有量（単位：質量％）を得る。
結着材がポリフッ化ビニリデン（ＰＶＤＦ：モノマー（ＣＨ２ＣＦ２）の分子量６４）である場合は、管状式燃焼法による燃焼イオンクロマトグラフィーにより測定されたフッ化物イオン（Ｆ－）の含有量（単位：質量％）、ＰＶＤＦを構成するモノマーのフッ素の原子量（１９）、及びＰＶＤＦを構成する炭素の原子量（１２）から以下の式で計算することができる。
ＰＶＤＦの含有量（単位：質量％）＝フッ化物イオンの含有量（単位：質量％）×６４／３８
ＰＶＤＦ由来の炭素の含有量Ｍ４（単位：質量％）＝フッ化物イオンの含有量（単位：質量％）×１２／１９
結着材がポリフッ化ビニリデンであることは、試料、又は試料をＮ，Ｎ－ジメチルホルムアミド（ＤＭＦ）溶媒により抽出した液体をフーリエ変換赤外スペクトル（ＦＴ－ＩＲ）測定し、Ｃ－Ｆ結合由来の吸収を確認する方法で確かめることができる。同様に１９Ｆ－ＮＭＲ測定でも確かめることができる。
結着材がＰＶＤＦ以外と同定された場合は、その分子量に相当する結着材の含有量（単位：質量％）および炭素の含有量（単位：質量％）を求めることで、結着材由来の炭素量Ｍ４を算出できる。
分散剤が含まれる場合は、前記Ｍ３からＭ４を減算し、さらに分散剤由来の炭素量を減算して導電性炭素の含有量（単位：質量％）を得ることができる。 [Measurement method C]
The total carbon content M3 (unit: % by mass) contained in the sample is measured in the same manner as in the measurement method B above. Also, the binder-derived carbon content M4 (unit: % by mass) is determined by the following method. Subtract M4 from M3 to obtain the conductive carbon content (unit: % by mass).
When the binder is polyvinylidene fluoride (PVDF: monomer (CH 2 CF 2 ) molecular weight 64), the content of fluoride ions (F − ) measured by combustion ion chromatography using a tubular combustion method ( Unit: % by mass), the fluorine atomic weight (19) of the monomer constituting PVDF, and the atomic weight (12) of carbon constituting PVDF by the following formula.
PVDF content (unit: mass%) = fluoride ion content (unit: mass%) x 64/38
PVDF-derived carbon content M4 (unit: mass%) = fluoride ion content (unit: mass%) x 12/19
The fact that the binder is polyvinylidene fluoride is obtained by measuring the sample or the liquid obtained by extracting the sample with an N,N-dimethylformamide (DMF) solvent by Fourier transform infrared spectrum (FT-IR), can be confirmed by a method for confirming the absorption of It can also be confirmed by 19 F-NMR measurement.
If the binder is identified to be other than PVDF, the content of the binder (unit: mass %) corresponding to the molecular weight and the content of carbon (unit: mass %) of carbon content M4 can be calculated.
When a dispersant is included, the content of conductive carbon (unit: mass %) can be obtained by subtracting M4 from M3 and further subtracting the amount of carbon derived from the dispersant.

正極活物質の組成などに応じて、［測定方法Ａ］～［測定方法Ｃ］から適切な方法を選択して導電性炭素の含有量を求めることができるが、汎用性などの観点から、［測定方法Ｂ］により導電性炭素の含有量を求めることが好ましい。
これらの手法は下記複数の公知文献に記載されている。
東レリサーチセンター Ｔｈｅ ＴＲＣ Ｎｅｗｓ Ｎｏ．１１７ （Ｓｅｐ．２０１３）第３４～３７頁、［２０２１年２月１０日検索］、インターネット＜https://www.toray-research.co.jp/technical-info/trcnews/pdf/TRC117(34-37).pdf＞
東ソー分析センター 技術レポート Ｎｏ．Ｔ１０１９ ２０１７．０９．２０、［２０２１年２月１０日検索］、インターネット＜http://www.tosoh-arc.co.jp/techrepo/files/tarc00522/T1719N.pdf＞ Depending on the composition of the positive electrode active material, etc., the content of conductive carbon can be determined by selecting an appropriate method from [Measurement method A] to [Measurement method C]. It is preferable to determine the content of conductive carbon by measuring method B].
These techniques are described in the following publications.
Toray Research Center The TRC News No. 117 (Sep. 2013) pp. 34-37, [searched on February 10, 2021], Internet <https://www.toray-research.co.jp/technical-info/trcnews/pdf/TRC117(34- 37).pdf＞
Tosoh Analysis Center Technical Report No. T1019 2017.09.20, [searched on February 10, 2021], Internet <http://www.tosoh-arc.co.jp/techrepo/files/tarc00522/T1719N.pdf>

≪導電性炭素の分析方法≫
正極活物質の活物質被覆部を構成する導電性炭素と、導電助剤である導電性炭素は、以下の分析方法で区別できる。
例えば、正極活物質層中の粒子を透過電子顕微鏡電子エネルギー損失分光法（ＴＥＭ－ＥＥＬＳ）により分析し、粒子表面近傍にのみ２９０ｅＶ付近の炭素由来のピークが存在する粒子は正極活物質であり、粒子内部にまで炭素由来のピークが存在する粒子は導電助剤と判定することができる。ここで「粒子表面近傍」とは、粒子表面からの深さが、約１００ｎｍまでの領域を意味し、「粒子内部」とは前記粒子表面近傍よりも内側の領域を意味する。
他の方法としては、正極活物質層中の粒子をラマン分光によりマッピング解析し、炭素由来のＧ－ｂａｎｄとＤ－ｂａｎｄ、及び正極活物質由来の酸化物結晶のピークが同時に観測された粒子は正極活物質であり、Ｇ－ｂａｎｄとＤ－ｂａｎｄのみが観測された粒子は導電助剤と判定することができる。
さらに他の方法としては、拡がり抵抗顕微鏡（ＳＳＲＭ：Ｓｃａｎｎｉｎｇ Ｓｐｒｅａｄ Ｒｅｓｉｓｔａｎｃｅ Ｍｉｃｒｏｓｃｏｐｅ）により、正極活物質層の断面を観察し、粒子表面に粒子内部より抵抗が低い部分が存在する場合、抵抗が低い部分は活物質被覆部に存在する導電性炭素であると判定できる。そのような粒子以外に独立して存在し、かつ抵抗が低い部分は導電助剤であると判定することができる。
なお、不純物として考えられる微量な炭素や、製造時に正極活物質の表面から意図せず剥がれた微量な炭素などは、導電助剤と判定しない。
これらの方法を用いて、炭素材料からなる導電助剤が正極活物質層に含まれるか否かを確認することができる。 <<Method for analyzing conductive carbon>>
The conductive carbon that constitutes the active material coating portion of the positive electrode active material and the conductive carbon that is the conductive aid can be distinguished by the following analysis method.
For example, the particles in the positive electrode active material layer are analyzed by transmission electron microscope electron energy loss spectroscopy (TEM-EELS), and particles having a carbon-derived peak near 290 eV only in the vicinity of the particle surface are positive electrode active materials, Particles in which carbon-derived peaks are present even inside the particles can be determined as conductive aids. Here, "near the particle surface" means a region up to about 100 nm deep from the particle surface, and "inside the particle" means a region inside the vicinity of the particle surface.
As another method, the particles in the positive electrode active material layer are subjected to mapping analysis by Raman spectroscopy. Particles that are positive electrode active materials and in which only the G-band and D-band are observed can be determined as conductive aids.
As yet another method, a scanning spread resistance microscope (SSRM) is used to observe the cross section of the positive electrode active material layer. It can be determined that it is the conductive carbon existing in the active material coating portion. It can be determined that a portion that exists independently and has a low resistance other than such particles is the conductive aid.
A small amount of carbon considered as an impurity, a small amount of carbon unintentionally peeled off from the surface of the positive electrode active material during production, and the like are not determined to be conductive aids.
Using these methods, it is possible to confirm whether or not the positive electrode active material layer contains a conductive aid made of a carbon material.

＜正極の製造方法＞
本実施形態の正極１の製造方法は、正極活物質を含む正極製造用組成物を調製する組成物調製工程と、正極製造用組成物を正極集電体１１上に塗工する塗工工程を有する。
例えば、正極活物質及び溶媒を含む正極製造用組成物を、正極集電体１１上に塗工し、乾燥し溶媒を除去して正極活物質層１２を形成する方法で正極１を製造できる。正極製造用組成物は導電助剤を含んでもよい。正極製造用組成物は結着材を含んでもよい。正極製造用組成物は分散剤を含んでもよい。
正極集電体１１上に正極活物質層１２を形成した積層物を、２枚の平板状冶具の間に挟み、厚み方向に均一に加圧する方法で、正極活物質層１２の厚みを調整できる。例えば、ロールプレス機を用いて加圧する方法を使用できる。 <Manufacturing method of positive electrode>
The method for manufacturing the positive electrode 1 of the present embodiment includes a composition preparation step of preparing a positive electrode manufacturing composition containing a positive electrode active material, and a coating step of applying the positive electrode manufacturing composition onto the positive electrode current collector 11. have.
For example, the positive electrode 1 can be manufactured by applying a positive electrode manufacturing composition containing a positive electrode active material and a solvent onto the positive electrode current collector 11 and drying it to remove the solvent to form the positive electrode active material layer 12 . The composition for positive electrode production may contain a conductive aid. The composition for manufacturing a positive electrode may contain a binder. The positive electrode manufacturing composition may contain a dispersant.
The thickness of the positive electrode active material layer 12 can be adjusted by a method in which a laminate in which the positive electrode active material layer 12 is formed on the positive electrode current collector 11 is sandwiched between two flat jigs and is evenly pressed in the thickness direction. . For example, a method of applying pressure using a roll press can be used.

正極製造用組成物の溶媒は非水系溶媒が好ましい。例えば、メタノール、エタノール、１－プロパノール、２－プロパノール等のアルコール；Ｎ－メチルピロリドン、Ｎ，Ｎ－ジメチルホルムアミド等の鎖状又は環状アミド；アセトン等のケトンが挙げられる。溶媒は１種でもよく、２種以上を併用してもよい。 A non-aqueous solvent is preferable as the solvent for the positive electrode-manufacturing composition. Examples include alcohols such as methanol, ethanol, 1-propanol and 2-propanol; linear or cyclic amides such as N-methylpyrrolidone and N,N-dimethylformamide; and ketones such as acetone. One type of solvent may be used, or two or more types may be used in combination.

正極製造用組成物中の正極活物質として、導電性炭素材料である活物質被覆部を有し、活物質被覆部の抵抗率が０．１５Ω・ｃｍ以上である正極活物質粒子を用いることが好ましい。正極活物質粒子の配合量は、正極製造用組成物の溶媒を除いた残りの質量に対して、活物質被覆部の含有量が０．９質量％以上となるように設定することが好ましい。正極製造用組成物が導電助剤を含まない場合、前記活物質被覆部の含有量は４．０質量％以下が好ましい。
正極製造用組成物が、前記正極活物質粒子に加えて、導電性炭素材料である導電助剤の１種以上を含む場合、正極製造用組成物の溶媒を除いた残りの質量に対して、抵抗率が０．１０Ω・ｃｍ以下である低抵抗の導電助剤の含有量が０．５質量％以下となるように、導電助剤の種類及び配合量を設定することが好ましい。また、正極製造用組成物の溶媒を除いた残りの質量に対して、活物質被覆部と導電助剤の合計の含有量が４．０質量％以下となるように、正極活物質粒子及び導電助剤の配合量を設定することが好ましい。 As the positive electrode active material in the composition for manufacturing a positive electrode, positive electrode active material particles having an active material coating portion made of a conductive carbon material and having a resistivity of 0.15 Ω·cm or more in the active material coating portion can be used. preferable. The amount of the positive electrode active material particles is preferably set so that the content of the active material coating portion is 0.9% by mass or more with respect to the remaining mass of the positive electrode manufacturing composition excluding the solvent. When the composition for positive electrode production does not contain a conductive aid, the content of the active material coating portion is preferably 4.0% by mass or less.
When the positive electrode-producing composition contains, in addition to the positive electrode active material particles, one or more conductive aids that are conductive carbon materials, the remaining mass of the positive electrode-producing composition excluding the solvent is It is preferable to set the type and blending amount of the conductive aid so that the content of the low-resistance conductive aid having a resistivity of 0.10 Ω·cm or less is 0.5% by mass or less. Further, the positive electrode active material particles and the conductive material are added so that the total content of the active material coating portion and the conductive aid is 4.0% by mass or less with respect to the remaining mass of the positive electrode manufacturing composition excluding the solvent. It is preferable to set the blending amount of the auxiliary agent.

＜非水電解質二次電池＞
図２に示す本実施形態の非水電解質二次電池１０は、本実施形態の非水電解質二次電池用正極１と、負極３と、非水電解質とを備える。さらにセパレータ２を備えてもよい。図中符号５は外装体である。
本実施形態において、正極１は、板状の正極集電体１１と、その両面上に設けられた正極活物質層１２と有する。正極活物質層１２は正極集電体１１の表面の一部に存在する。正極集電体１１の表面の縁部は、正極活物質層１２が存在しない正極集電体露出部１３である。正極集電体露出部１３の任意の箇所に、図示しない端子用タブが電気的に接続する。
負極３は、板状の負極集電体３１と、その両面上に設けられた負極活物質層３２とを有する。負極活物質層３２は負極集電体３１の表面の一部に存在する。負極集電体３１の表面の縁部は、負極活物質層３２が存在しない負極集電体露出部３３である。負極集電体露出部３３の任意の箇所に、図示しない端子用タブが電気的に接続する。
正極１、負極３およびセパレータ２の形状は特に限定されない。例えば平面視矩形状でもよい。
本実施形態の非水電解質二次電池１０は、例えば、正極１と負極３を、セパレータ２を介して交互に積層した電極積層体を作製し、電極積層体をアルミラミネート袋等の外装体（筐体）５に封入し、非水電解質（図示せず）を注入して密閉する方法で製造できる。 図２では、代表的に、負極／セパレータ／正極／セパレータ／負極の順に積層した構造を示しているが、電極の数は適宜変更できる。正極１は１枚以上あればよく、得ようとする電池容量に応じて任意の数の正極１を用いることができる。負極３及びセパレータ２は、正極１の数より１枚多く用い、最外層が負極３となるように積層する。 <Non-aqueous electrolyte secondary battery>
A non-aqueous electrolyte secondary battery 10 of the present embodiment shown in FIG. 2 includes the positive electrode 1 for non-aqueous electrolyte secondary batteries of the present embodiment, a negative electrode 3, and a non-aqueous electrolyte. Further, a separator 2 may be provided. Reference numeral 5 in the figure is an exterior body.
In this embodiment, the positive electrode 1 has a plate-like positive electrode current collector 11 and positive electrode active material layers 12 provided on both surfaces thereof. The positive electrode active material layer 12 exists on part of the surface of the positive electrode current collector 11 . An edge portion of the surface of the positive electrode current collector 11 is a positive electrode current collector exposed portion 13 where the positive electrode active material layer 12 does not exist. A terminal tab (not shown) is electrically connected to an arbitrary portion of the positive electrode current collector exposed portion 13 .
The negative electrode 3 has a plate-like negative electrode current collector 31 and negative electrode active material layers 32 provided on both sides thereof. The negative electrode active material layer 32 exists on part of the surface of the negative electrode current collector 31 . An edge portion of the surface of the negative electrode current collector 31 is a negative electrode current collector exposed portion 33 where the negative electrode active material layer 32 does not exist. A terminal tab (not shown) is electrically connected to an arbitrary portion of the negative electrode current collector exposed portion 33 .
The shapes of the positive electrode 1, the negative electrode 3 and the separator 2 are not particularly limited. For example, it may be rectangular in plan view.
The non-aqueous electrolyte secondary battery 10 of the present embodiment is produced, for example, by fabricating an electrode laminate by alternately laminating the positive electrode 1 and the negative electrode 3 with the separator 2 interposed therebetween. It can be manufactured by a method of enclosing in a housing 5, injecting a non-aqueous electrolyte (not shown), and sealing. FIG. 2 typically shows a structure in which negative electrodes/separators/positive electrodes/separators/negative electrodes are laminated in this order, but the number of electrodes can be changed as appropriate. One or more positive electrodes 1 are sufficient, and any number of positive electrodes 1 can be used according to the battery capacity to be obtained. One more negative electrode 3 and separator 2 than the number of positive electrodes 1 are used, and they are laminated so that the negative electrode 3 is the outermost layer.

［負極］
負極活物質層３２は負極活物質を含む。さらに結着材を含んでもよい。さらに導電助剤を含んでもよい。負極活物質の形状は、粒子状が好ましい。
負極３は、例えば、負極活物質、結着材、及び溶媒を含む負極製造用組成物を調製し、これを負極集電体３１上に塗工し、乾燥し溶媒を除去して負極活物質層３２を形成する方法で製造できる。負極製造用組成物は導電助剤を含んでもよい。 [Negative electrode]
The negative electrode active material layer 32 contains a negative electrode active material. Furthermore, a binding material may be included. Further, it may contain a conductive aid. The shape of the negative electrode active material is preferably particulate.
For the negative electrode 3, for example, a negative electrode manufacturing composition containing a negative electrode active material, a binder, and a solvent is prepared, the negative electrode current collector 31 is coated with the composition, and the solvent is removed by drying to remove the negative electrode active material. It can be manufactured by any method that forms layer 32 . The negative electrode production composition may contain a conductive aid.

負極活物質及び導電助剤としては、例えば炭素材料、チタン酸リチウム（ＬＴＯ）、シリコン、一酸化シリコン等が挙げられる。炭素材料としては、ケッチェンブラック、アセチレンブラック等のカーボンブラック、グラファイト、グラフェン、ハードカーボン、カーボンナノチューブ（ＣＮＴ）等が挙げられる。負極活物質及び導電助剤は、それぞれ１種でもよく２種以上を併用してもよい。 Examples of negative electrode active materials and conductive aids include carbon materials, lithium titanate (LTO), silicon, and silicon monoxide. Examples of carbon materials include carbon black such as ketjen black and acetylene black, graphite, graphene, hard carbon, and carbon nanotube (CNT). Each of the negative electrode active material and the conductive aid may be used alone or in combination of two or more.

負極集電体３１の材料は、上記した正極集電体１１の材料と同様のものを例示できる。 負極製造用組成物中の結着材としては、ポリアクリル酸（ＰＡＡ）、ポリアクリル酸リチウム（ＰＡＡＬｉ）、ポリフッ化ビニリデン（ＰＶＤＦ）、ポリフッ化ビニリデン－六フッ化プロピレン共重合体（ＰＶＤＦ－ＨＦＰ）、スチレンブタジエンゴム（ＳＢＲ）、ポリビニルアルコール（ＰＶＡ）、ポリエチレンオキサイド（ＰＥＯ）、ポリエチレングリコール（ＰＥＧ）、カルボキシメチルセルロース（ＣＭＣ）、ポリアクリルニトリル（ＰＡＮ）、ポリイミド（ＰＩ）等が例示できる。結着材は１種でもよく２種以上を併用してもよい。
負極製造用組成物中の溶媒としては、水、有機溶媒が例示できる。有機溶媒としては、メタノール、エタノール、１－プロパノール、２－プロパノール等のアルコール；Ｎ－メチルピロリドン（ＮＭＰ）、Ｎ，Ｎ－ジメチルホルムアミド（ＤＭＦ）等の鎖状又は環状アミド；アセトン等のケトンが例示できる。溶媒は１種でもよく２種以上を併用してもよい。 The material of the negative electrode current collector 31 can be exemplified by the same materials as those of the positive electrode current collector 11 described above. Binders in the negative electrode production composition include polyacrylic acid (PAA), lithium polyacrylate (PAALi), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-propylene hexafluoride copolymer (PVDF-HFP ), styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), polyethylene oxide (PEO), polyethylene glycol (PEG), carboxymethylcellulose (CMC), polyacrylonitrile (PAN), polyimide (PI), and the like. One type of binder may be used, or two or more types may be used in combination.
Examples of the solvent in the negative electrode-producing composition include water and organic solvents. Organic solvents include alcohols such as methanol, ethanol, 1-propanol and 2-propanol; linear or cyclic amides such as N-methylpyrrolidone (NMP) and N,N-dimethylformamide (DMF); and ketones such as acetone. I can give an example. The solvent may be used alone or in combination of two or more.

負極活物質層３２の総質量に対して、負極活物質及び導電助剤の合計の含有量は８０．０～９９．９質量％が好ましく、８５．０～９８．０質量％がより好ましい。 The total content of the negative electrode active material and the conductive aid is preferably 80.0 to 99.9 mass %, more preferably 85.0 to 98.0 mass %, relative to the total mass of the negative electrode active material layer 32 .

［セパレータ］
セパレータ２を負極３と正極１との間に配置して短絡等を防止する。セパレータ２は、後述する非水電解質を保持してもよい。
セパレータ２としては、特に限定されず、多孔性の高分子膜、不織布、ガラスファイバー等が例示できる。
セパレータ２の一方又は両方の表面上に絶縁層を設けてもよい。絶縁層は、絶縁性微粒子を絶縁層用結着材で結着した多孔質構造を有する層が好ましい。 [Separator]
A separator 2 is arranged between the negative electrode 3 and the positive electrode 1 to prevent short circuit or the like. The separator 2 may hold a non-aqueous electrolyte, which will be described later.
The separator 2 is not particularly limited, and can be exemplified by porous polymer membranes, non-woven fabrics, glass fibers, and the like.
An insulating layer may be provided on one or both surfaces of the separator 2 . The insulating layer is preferably a layer having a porous structure in which insulating fine particles are bound with an insulating layer binder.

セパレータ２は、各種可塑剤、酸化防止剤、難燃剤を含んでもよい。
酸化防止剤としては、ヒンダードフェノール系酸化防止剤、モノフェノール系酸化防止剤、ビスフェノール系酸化防止剤、ポリフェノール系酸化防止剤等のフェノール系酸化防止剤；ヒンダードアミン系酸化防止剤；リン系酸化防止剤；イオウ系酸化防止剤；ベンゾトリアゾール系酸化防止剤；ベンゾフェノン系酸化防止剤；トリアジン系酸化防止剤；サルチル酸エステル系酸化防止剤等が例示できる。フェノール系酸化防止剤、リン系酸化防止剤が好ましい。 The separator 2 may contain various plasticizers, antioxidants and flame retardants.
Antioxidants include phenolic antioxidants such as hindered phenolic antioxidants, monophenolic antioxidants, bisphenolic antioxidants, and polyphenolic antioxidants; hindered amine antioxidants; phosphorus antioxidants. benzotriazole-based antioxidants; benzophenone-based antioxidants; triazine-based antioxidants; salicylic acid ester-based antioxidants, and the like. Phenolic antioxidants and phosphorus antioxidants are preferred.

［非水電解質］
非水電解質は正極１と負極３との間を満たす。例えば、リチウムイオン二次電池、電気二重層キャパシタ等において公知の非水電解質を使用できる。
非水電解質として、有機溶媒に電解質塩を溶解した非水電解液が好ましい。 [Non-aqueous electrolyte]
A non-aqueous electrolyte fills between the positive electrode 1 and the negative electrode 3 . For example, known nonaqueous electrolytes can be used in lithium ion secondary batteries, electric double layer capacitors and the like.
As the non-aqueous electrolyte, a non-aqueous electrolytic solution obtained by dissolving an electrolyte salt in an organic solvent is preferable.

有機溶媒は、高電圧に対する耐性を有するものが好ましい。例えば、エチレンカーボネート、プロピレンカーボネート、ジメチルカーボネート、ジエチルカーボネート、エチルメチルカーボネート、γ－ブチロラクトン、スルホラン、ジメチルスルホキシド、アセトニトリル、ジメチルホルムアミド、ジメチルアセトアミド、１，２－ジメトキシエタン、１，２－ジエトキシエタン、テトロヒドラフラン、２－メチルテトラヒドロフラン、ジオキソラン、メチルアセテート等の極性溶媒、又はこれら極性溶媒の２種類以上の混合物が挙げられる。 The organic solvent preferably has resistance to high voltage. For example, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, sulfolane, dimethyl sulfoxide, acetonitrile, dimethylformamide, dimethylacetamide, 1,2-dimethoxyethane, 1,2-diethoxyethane, Polar solvents such as tetrahydrafuran, 2-methyltetrahydrofuran, dioxolane, methyl acetate, or mixtures of two or more of these polar solvents are included.

電解質塩は、特に限定されず、例えばＬｉＣｌＯ４、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＡｓＦ６、ＬｉＣＦ６、ＬｉＣＦ３ＣＯ２、ＬｉＰＦ６ＳＯ３、ＬｉＮ（ＳＯ２Ｆ）２、ＬｉＮ（ＳＯ２ＣＦ３）２、Ｌｉ（ＳＯ２ＣＦ２ＣＦ３）２、ＬｉＮ（ＣＯＣＦ３）２、ＬｉＮ（ＣＯＣＦ２ＣＦ３）２等のリチウムを含む塩、又はこれら塩の２種以上の混合物が挙げられる。 The electrolyte salt is not particularly limited, and examples thereof include LiClO 4 , LiPF 6 , LiBF 4 , LiAsF 6 , LiCF 6 , LiCF 3 CO 2 , LiPF 6 SO 3 , LiN(SO 2 F) 2 and LiN(SO 2 CF 3 ). 2 , Li( SO2CF2CF3 ) 2 , LiN ( COCF3 ) 2 , LiN( COCF2CF3 ) 2 , or a mixture of two or more of these salts.

本実施形態の非水電解質二次電池は、産業用、民生用、自動車用、住宅用等、各種用途のリチウムイオン二次電池として使用できる。
本実施形態の非水電解質二次電池の使用形態は特に限定されない。例えば、複数個の非水電解質二次電池を直列又は並列に接続して構成した電池モジュール、電気的に接続した複数個の電池モジュールと電池制御システムとを備える電池システム等に用いることができる。
電池システムの例としては、電池パック、定置用蓄電池システム、自動車の動力用蓄電池システム、自動車の補機用蓄電池システム、非常電源用蓄電池システム等が挙げられる。 The non-aqueous electrolyte secondary battery of the present embodiment can be used as a lithium ion secondary battery for various uses such as industrial use, consumer use, automobile use, and residential use.
The mode of use of the non-aqueous electrolyte secondary battery of this embodiment is not particularly limited. For example, it can be used in a battery module configured by connecting a plurality of nonaqueous electrolyte secondary batteries in series or in parallel, a battery system including a plurality of electrically connected battery modules and a battery control system, and the like.
Examples of battery systems include battery packs, stationary storage battery systems, automotive power storage battery systems, automotive auxiliary equipment storage battery systems, and emergency power supply storage battery systems.

－ 第３の実施形態 －
本発明の第３の実施形態に係る非水電解質二次電池用正極１は、正極集電体１１と、前記正極集電体１１上に存在する正極活物質層１２とを有し、前記正極活物質層１２が正極活物質を含み、前記正極活物質の表面の少なくとも一部に、導電材料を含む活物質被覆部が存在し、前記正極活物質層の粉体抵抗率が１０～１，０００Ω・ｃｍである。
上記構成を有する非水電解質二次電池用正極１は、正極活物質層１２の剥離強度が良好であり、非水電解質二次電池のインピーダンスを低減できる。
以下に具体的に説明する。 - Third Embodiment -
A positive electrode 1 for a non-aqueous electrolyte secondary battery according to a third embodiment of the present invention has a positive electrode current collector 11 and a positive electrode active material layer 12 present on the positive electrode current collector 11, and the positive electrode The active material layer 12 contains a positive electrode active material, an active material coating portion containing a conductive material is present on at least part of the surface of the positive electrode active material, and the powder resistivity of the positive electrode active material layer is 10 to 1. 000Ω·cm.
In the positive electrode 1 for a non-aqueous electrolyte secondary battery having the above configuration, the peel strength of the positive electrode active material layer 12 is good, and the impedance of the non-aqueous electrolyte secondary battery can be reduced.
A specific description will be given below.

［正極活物質層］
正極活物質層１２は正極活物質を含む。正極活物質層１２は、さらに結着材を含むことが好ましい。正極活物質層１２は、さらに導電助剤を含んでもよい。
正極活物質の形状は、粒子状が好ましい。
正極活物質層１２の総質量に対して、正極活物質の含有量は８０．０～９９．９質量％が好ましく、９０～９９．５質量％がより好ましい。 [Positive electrode active material layer]
The positive electrode active material layer 12 contains a positive electrode active material. The positive electrode active material layer 12 preferably further contains a binder. The positive electrode active material layer 12 may further contain a conductive aid.
The shape of the positive electrode active material is preferably particulate.
The content of the positive electrode active material is preferably 80.0 to 99.9% by mass, more preferably 90 to 99.5% by mass, based on the total mass of the positive electrode active material layer 12 .

正極活物質の表面の少なくとも一部には、導電材料を含む活物質被覆部が存在する（活物質被覆部を有する正極活物質粒子を、以下、「被覆粒子」と称することもある）。活物質被覆部の導電材料は、炭素を含むことが好ましい。炭素のみからなる導電材料でもよく、炭素と炭素以外の他の元素とを含む導電性有機化合物でもよい。他の元素としては、窒素、水素、酸素等が例示できる。前記導電性有機化合物において、他の元素は１０原子％以下が好ましく、５原子％以下がより好ましい。
活物質被覆部を構成する導電材料は、炭素のみからなることがさらに好ましい。
活物質被覆部を有する正極活物質の総質量に対して、導電材料の含有量は０．１～３．０質量％が好ましく、０．５～１．５質量％がより好ましく、０．７～１．３質量％がさらに好ましい。 At least part of the surface of the positive electrode active material has an active material coating portion containing a conductive material (a positive electrode active material particle having an active material coating portion may be hereinafter referred to as a “coated particle”). The conductive material of the active material coating preferably contains carbon. A conductive material consisting only of carbon may be used, or a conductive organic compound containing carbon and an element other than carbon may be used. Nitrogen, hydrogen, oxygen and the like can be exemplified as other elements. In the conductive organic compound, the content of other elements is preferably 10 atomic % or less, more preferably 5 atomic % or less.
It is more preferable that the conductive material forming the active material coating portion consist of carbon only.
The content of the conductive material is preferably 0.1 to 3.0% by mass, more preferably 0.5 to 1.5% by mass, and 0.7 based on the total mass of the positive electrode active material having the active material coating. ~1.3% by mass is more preferred.

被覆粒子において、正極活物質粒子の表面には、導電材料を含む被覆部（以下、「活物質被覆部」ともいう。）が存在する。正極活物質粒子は、活物質被覆部を有することで、電池容量、サイクル特性をより高められる。
例えば、活物質被覆部は、予め正極活物質粒子の表面に形成されており、かつ正極活物質層中において、正極活物質粒子の表面に存在する。即ち、本稿における活物質被覆部は、正極製造用組成物の調製段階以降の工程で新たに形成されるものではない。加えて、活物質被覆部は、正極製造用組成物の調製段階以降の工程で欠落するものではない。
例えば、正極製造用組成物を調製する際に、被覆粒子を溶媒と共にミキサー等で混合しても、活物質被覆部は正極活物質の表面を被覆している。また、仮に、正極から正極活物質層を剥がし、これを溶媒に投入して正極活物質層中の結着材を溶媒に溶解させた場合にも、活物質被覆部は正極活物質の表面を被覆している。また、仮に、正極活物質層中の粒子の粒度分布をレーザー回折・散乱法により測定する際に、凝集した粒子をほぐす操作を行った場合にも活物質被覆部は正極活物質の表面を被覆している。
活物質被覆部は、正極活物質粒子の外表面全体の面積の５０％以上に存在することが好ましく、７０％以上に存在することが好ましく、９０％以上に存在することが好ましい。
すなわち、被覆粒子は、正極活物質である芯部と、前記芯部の表面を覆う活物質被覆部とを有し、芯部の表面積に対する活物質被覆部の面積（被覆率）は、５０％以上が好ましく、７０％以上がより好ましく、９０％以上がさらに好ましい。 In the coated particles, a coating portion containing a conductive material (hereinafter also referred to as “active material coating portion”) is present on the surface of the positive electrode active material particle. Since the positive electrode active material particles have the active material coating portion, the battery capacity and cycle characteristics can be further improved.
For example, the active material coating portion is formed in advance on the surfaces of the positive electrode active material particles, and is present on the surfaces of the positive electrode active material particles in the positive electrode active material layer. That is, the active material coating portion in this specification is not newly formed in the steps after the step of preparing the composition for manufacturing a positive electrode. In addition, the active material coating portion does not fall off in the steps after the step of preparing the composition for manufacturing a positive electrode.
For example, even when the coated particles are mixed with a solvent in a mixer or the like when preparing the positive electrode-manufacturing composition, the active material-coating portion still covers the surface of the positive electrode active material. Further, even if the positive electrode active material layer is peeled off from the positive electrode and put into a solvent to dissolve the binder in the positive electrode active material layer in the solvent, the active material coating part covers the surface of the positive electrode active material. covered. In addition, even if the particle size distribution of the particles in the positive electrode active material layer is measured by a laser diffraction/scattering method, even if an operation is performed to loosen the aggregated particles, the active material coating portion covers the surface of the positive electrode active material. are doing.
The active material coating portion preferably exists in 50% or more, preferably 70% or more, and preferably 90% or more of the entire outer surface area of the positive electrode active material particles.
That is, the coated particles have a core that is a positive electrode active material and an active material coating that covers the surface of the core, and the area (coverage) of the active material coating with respect to the surface area of the core is 50%. 70% or more is more preferable, and 90% or more is even more preferable.

被覆粒子の製造方法としては、例えば、焼結法、蒸着法等が挙げられる。
焼結法としては、正極活物質の粒子と有機物とを含む活物質製造用組成物（例えば、スラリー）を、大気圧下、５００～１０００℃、１～１００時間で焼成する方法が挙げられる。活物質製造用組成物に添加する有機物としては、サリチル酸、カテコール、ヒドロキノン、レゾルシノール、ピロガロール、フロログルシノール、ヘキサヒドロキシベンゼン、安息香酸、フタル酸、テレフタル酸、フェニルアラニン、水分散型フェノール樹脂等、スクロース、グルコース、ラクトース等の糖類、リンゴ酸、クエン酸などのカルボン酸、アリルアルコール、プロパルギルアルコール等の不飽和一価アルコール、アスコルビン酸、ポリビニルアルコール等が挙げられる。この焼結法によれば、活物質製造用組成物を焼成することで、有機物中の炭素を正極活物質の表面に焼結して、活物質被覆部を形成する。
また、他の焼結法としては、いわゆる衝撃焼結被覆法が挙げられる。 Examples of the method for producing coated particles include a sintering method and a vapor deposition method.
Examples of the sintering method include a method in which a composition for producing an active material (eg, slurry) containing positive electrode active material particles and an organic substance is fired at 500 to 1000° C. for 1 to 100 hours under atmospheric pressure. Examples of organic substances added to the active material-producing composition include salicylic acid, catechol, hydroquinone, resorcinol, pyrogallol, phloroglucinol, hexahydroxybenzene, benzoic acid, phthalic acid, terephthalic acid, phenylalanine, water-dispersed phenolic resin, and sucrose. , glucose and lactose, carboxylic acids such as malic acid and citric acid, unsaturated monohydric alcohols such as allyl alcohol and propargyl alcohol, ascorbic acid, and polyvinyl alcohol. According to this sintering method, the carbon in the organic matter is sintered onto the surface of the positive electrode active material by firing the active material-producing composition to form the active material coating portion.
Another sintering method is the so-called impact sinter coating method.

衝撃焼結被覆法は、例えば、衝撃焼結被覆装置において燃料の炭化水素と酸素の混合ガスを用いてバーナに点火し燃焼室で燃焼させてフレームを発生させ、その際、酸素量を燃料に対して完全燃焼の当量以下にしてフレーム温度を下げ、その後方に粉末供給用ノズルを設置し、そのノズルから被覆する有機物と溶媒を用いて溶かしスラリー状にしたものと燃焼ガスからなる固体―液体―気体三相混合物を粉末供給ノズルから噴射させ、室温に保持された燃焼ガス量を増して、噴射微粉末の温度を下げて、粉末材料の変態温度、昇華温度、蒸発温度以下で加速し、衝撃により瞬時焼結させて、正極活物質の粒子を被覆する。
蒸着法としては、物理気相成長法（ＰＶＤ）、化学気相成長法（ＣＶＤ）等の気相堆積法、メッキ等の液相堆積法等が挙げられる。 In the impact sintering coating method, for example, in an impact sintering coating device, a mixed gas of hydrocarbon and oxygen as a fuel is used to ignite a burner and burn it in a combustion chamber to generate a flame. On the other hand, the flame temperature is lowered to below the equivalent of complete combustion, and a powder supply nozzle is installed behind it, and the solid-liquid consisting of the organic matter to be coated and the slurry melted using the solvent and the combustion gas from the nozzle. - Injecting the gaseous three-phase mixture from the powder feed nozzle, increasing the amount of combustion gas maintained at room temperature, lowering the temperature of the injected fine powder, and accelerating it below the transformation temperature, sublimation temperature, and evaporation temperature of the powder material, Instantly sintered by impact to coat the particles of the positive electrode active material.
Vapor deposition methods include physical vapor deposition (PVD), chemical vapor deposition (CVD) and other vapor phase deposition methods, and liquid phase deposition methods such as plating.

前記被覆率は次の様な方法により測定することができる。まず、正極活物質層中の粒子を透過電子顕微鏡を用いたエネルギー分散型Ｘ線分光法（ＴＥＭ－ＥＤＸ）により分析する。具体的には、ＴＥＭ画像における正極活物質粒子の外周部をＥＤＸで元素分析する。元素分析は炭素について行い、正極活物質粒子を被覆している炭素を特定する。炭素の被覆部が１ｎｍ以上の厚さである箇所を被覆部分とし、観察した正極活物質粒子の全周に対して被覆部分の割合を求め、これを被覆率とすることができる。測定は例えば、１０個の正極活物質粒子について行い、これらの平均値とすることができる。
また、前記活物質被覆部は、正極活物質のみから構成される粒子（以下、「芯部」と称することもある。）の表面上に直接形成された厚み１ｎｍ～１００ｎｍ、好ましくは５ｎｍ～５０ｎｍの層であり、この厚みは上述した被覆率の測定に用いるＴＥＭ－ＥＤＸによって確認することができる。 The coverage can be measured by the following method. First, particles in the positive electrode active material layer are analyzed by energy dispersive X-ray spectroscopy (TEM-EDX) using a transmission electron microscope. Specifically, the outer peripheral portion of the positive electrode active material particles in the TEM image is subjected to elemental analysis by EDX. Elemental analysis is performed on carbon to identify the carbon coating the positive electrode active material particles. A portion where the carbon-covered portion has a thickness of 1 nm or more is defined as a covered portion, and the ratio of the covered portion to the entire circumference of the observed positive electrode active material particles can be obtained and used as the coverage rate. For example, 10 positive electrode active material particles are measured, and the average value thereof can be obtained.
In addition, the active material coating part is formed directly on the surface of a particle (hereinafter sometimes referred to as "core part") composed only of the positive electrode active material and has a thickness of 1 nm to 100 nm, preferably 5 nm to 50 nm. This thickness can be confirmed by TEM-EDX used for the measurement of the coverage rate described above.

本発明において、被覆粒子は、芯部の表面積に対する活物質被覆部の面積は、１００％が特に好ましい。
なお、この被覆率（％）は、正極活物質層中に存在する正極活物質粒子全体についての平均値であり、この平均値が上記下限値以上となる限り、活物質被覆部を有しない正極活物質粒子が微量に存在することを排除するものではない。活物質被覆部を有しない正極活物質粒子（単一粒子）が正極活物質層中に存在する場合、その量は、正極活物質層中に存在する正極活物質粒子全体の量に対して、好ましくは３０質量％以下であり、より好ましくは２０質量％以下であり、特に好ましくは１０質量％以下である。 In the present invention, it is particularly preferable that the area of the active material-coated portion with respect to the surface area of the core portion of the coated particles is 100%.
Note that this coverage (%) is the average value for all the positive electrode active material particles present in the positive electrode active material layer, and as long as this average value is equal to or higher than the above lower limit, the positive electrode without the active material coating portion It does not exclude the presence of a very small amount of active material particles. When positive electrode active material particles (single particles) having no active material coating part are present in the positive electrode active material layer, the amount thereof is, relative to the total amount of positive electrode active material particles present in the positive electrode active material layer, It is preferably 30% by mass or less, more preferably 20% by mass or less, and particularly preferably 10% by mass or less.

正極活物質は、オリビン型結晶構造を有する化合物を含むことが好ましい。
オリビン型結晶構造を有する化合物は、一般式ＬｉＦｅｘＭ（１－ｘ）ＰＯ４で（以下「一般式（Ｉ）」ともいう。）表される化合物が好ましい。一般式（Ｉ）において０≦ｘ≦１である。ＭはＣｏ、Ｎｉ、Ｍｎ、Ａｌ、Ｔｉ又はＺｒである。物性値に変化がない程度に微小量の、ＦｅおよびＭ（Ｃｏ、Ｎｉ、Ｍｎ、Ａｌ、Ｔｉ又はＺｒ）の一部を他の元素に置換することもできる。一般式（Ｉ）で表される化合物は、微量の金属不純物が含まれていても本発明の効果が損なわれるものではない。 The positive electrode active material preferably contains a compound having an olivine crystal structure.
A compound having an olivine-type crystal structure is preferably a compound represented by the general formula LiFe x M (1-x) PO 4 (hereinafter also referred to as “general formula (I)”). 0≦x≦1 in general formula (I). M is Co, Ni, Mn, Al, Ti or Zr. A small amount of Fe and M (Co, Ni, Mn, Al, Ti or Zr) can be substituted with other elements to the extent that the physical properties are not changed. Even if the compound represented by the general formula (I) contains a trace amount of metal impurities, the effect of the present invention is not impaired.

一般式（Ｉ）で表される化合物は、ＬｉＦｅＰＯ４で表されるリン酸鉄リチウム（以下、単に「リン酸鉄リチウム」ともいう。）が好ましい。表面の少なくとも一部に導電材料を含む活物質被覆部が存在するリン酸鉄リチウム（以下「被覆リン酸鉄リチウム」ともいう。）がより好ましい。電池容量、サイクル特性により優れる点から、リン酸鉄リチウムの表面全体が導電材料で被覆されていることがさらに好ましい。
被覆リン酸鉄リチウムは公知の方法で製造できる。
例えば、特許第５０９８１４６号公報に記載の方法を用いてリン酸鉄リチウム粉末を作製し、ＧＳ Ｙｕａｓａ Ｔｅｃｈｎｉｃａｌ Ｒｅｐｏｒｔ、２００８年６月、第５巻、第１号、第２７～３１頁等に記載の方法を用いて、リン酸鉄リチウム粉末の表面の少なくとも一部を炭素で被覆できる。
具体的には、まず、シュウ酸鉄二水和物、リン酸二水素アンモニウム、及び炭酸リチウムを、特定のモル比で計り、これらを不活性雰囲気下で粉砕及び混合する。次に、得られた混合物を窒素雰囲気下で加熱処理することによってリン酸鉄リチウム粉末を作製する。次いで、リン酸鉄リチウム粉末をロータリーキルンに入れ、窒素をキャリアガスとしたメタノール蒸気を供給しながら加熱処理することによって、表面の少なくとも一部を炭素で被覆したリン酸鉄リチウム粉末を得る。
例えば、粉砕工程における粉砕時間によってリン酸鉄リチウム粉末の粒子径を調整できる。メタノール蒸気を供給しながら加熱処理する工程における加熱時間及び温度等によって、リン酸鉄リチウム粉末を被覆する炭素の量を調整できる。被覆されなかった炭素粒子はその後の分級や洗浄などの工程などにより取り除くことが望ましい。 The compound represented by the general formula (I) is preferably lithium iron phosphate represented by LiFePO 4 (hereinafter also simply referred to as “lithium iron phosphate”). Lithium iron phosphate (hereinafter also referred to as “coated lithium iron phosphate”) having an active material coating portion containing a conductive material on at least a part of the surface is more preferable. It is more preferable that the entire surface of the lithium iron phosphate is coated with a conductive material from the viewpoint of better battery capacity and cycle characteristics.
Coated lithium iron phosphate can be produced by a known method.
For example, lithium iron phosphate powder is prepared using the method described in Japanese Patent No. 5098146, and described in GS Yuasa Technical Report, June 2008, Vol. 5, No. 1, pp. 27-31. The method can be used to coat at least a portion of the surface of the lithium iron phosphate powder with carbon.
Specifically, first, iron oxalate dihydrate, ammonium dihydrogen phosphate, and lithium carbonate are weighed in a specific molar ratio, and these are pulverized and mixed under an inert atmosphere. Next, a lithium iron phosphate powder is produced by heat-treating the obtained mixture in a nitrogen atmosphere. Next, the lithium iron phosphate powder is placed in a rotary kiln and heat-treated while supplying methanol vapor using nitrogen as a carrier gas to obtain a lithium iron phosphate powder having at least a portion of the surface coated with carbon.
For example, the particle size of the lithium iron phosphate powder can be adjusted by adjusting the pulverization time in the pulverization step. The amount of carbon covering the lithium iron phosphate powder can be adjusted by the heating time and temperature in the step of heat-treating while supplying methanol vapor. It is desirable to remove uncoated carbon particles by subsequent steps such as classification and washing.

正極活物質は、オリビン型結晶構造を有する化合物以外の他の正極活物質を含んでもよい。
他の正極活物質は、リチウム遷移金属複合酸化物が好ましい。例えば、コバルト酸リチウム（ＬｉＣｏＯ２）、ニッケル酸リチウム（ＬｉＮｉＯ２）、ニッケルコバルト酸リチウム（ＬｉＮｉｘＣｏｙＡｌｚＯ２、ただしｘ＋ｙ＋ｚ＝１）、ニッケルコバルトマンガン酸リチウム（ＬｉＮｉｘＣｏｙＭｎｚＯ２、ただしｘ＋ｙ＋ｚ＝１）、マンガン酸リチウム（ＬｉＭｎ２Ｏ４）、コバルトマンガン酸リチウム（ＬｉＭｎＣｏＯ４）、クロム酸マンガンリチウム（ＬｉＭｎＣｒＯ４）、バナジウムニッケル酸リチウム（ＬｉＮｉＶＯ４）、ニッケル置換マンガン酸リチウム（例えば、ＬｉＭｎ１．５Ｎｉ０．５Ｏ４）、及びバナジウムコバルト酸リチウム（ＬｉＣｏＶＯ４）、これらの化合物の一部を金属元素で置換した非化学量論的化合物等が挙げられる。前記金属元素としては、Ｍｎ、Ｍｇ、Ｎｉ、Ｃｏ、Ｃｕ、Ｚｎ及びＧｅからなる群から選択される１種以上が挙げられる。
他の正極活物質は１種でもよく、２種以上でもよい。
他の正極活物質は、表面の少なくとも一部に前記活物質被覆部が存在してもよい。 The positive electrode active material may contain a positive electrode active material other than the compound having an olivine crystal structure.
Another positive electrode active material is preferably a lithium transition metal composite oxide. For example, lithium cobalt oxide (LiCoO 2 ), lithium nickel oxide ( LiNiO 2 ) , lithium nickel cobalt oxide ( LiNixCoyAlzO2 , where x + y+z=1), lithium nickel cobalt manganate ( LiNixCoyMnz O 2 , where x+y+z=1), lithium manganate (LiMn 2 O 4 ), lithium cobalt manganate (LiMnCoO 4 ), lithium manganese chromate (LiMnCrO 4 ), lithium vanadium nickelate (LiNiVO 4 ), nickel-substituted manganates Lithium (for example, LiMn 1.5 Ni 0.5 O 4 ), lithium vanadium cobalt oxide (LiCoVO 4 ), non-stoichiometric compounds obtained by substituting a part of these compounds with metal elements, and the like. Examples of the metal element include one or more selected from the group consisting of Mn, Mg, Ni, Co, Cu, Zn and Ge.
1 type may be sufficient as another positive electrode active material, and 2 or more types may be sufficient as it.
Other positive electrode active materials may have the active material coating on at least part of the surface.

正極活物質の総質量に対して、オリビン型結晶構造を有する化合物の含有量は５０質量％以上が好ましく、８０質量％以上がより好ましく、９０質量％以上がさらに好ましい。１００質量％でもよい。
被覆リン酸鉄リチウムを用いる場合、正極活物質の総質量に対して、被覆リン酸鉄リチウムの含有量は５０質量％以上が好ましく、８０質量％以上がより好ましく、９０質量％以上がさらに好ましい。１００質量％でもよい。 The content of the compound having an olivine crystal structure is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, relative to the total mass of the positive electrode active material. 100 mass % may be sufficient.
When the coated lithium iron phosphate is used, the content of the coated lithium iron phosphate is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, relative to the total mass of the positive electrode active material. . 100 mass % may be sufficient.

正極活物質の活物質被覆部の厚さは、上述した通り、１～１００ｎｍが好ましい。
正極活物質の活物質被覆部の厚さは、上述した通り、正極活物質の透過電子顕微鏡（ＴＥＭ）像における活物質被覆部の厚さを計測する方法で測定できる。正極活物質の表面に存在する活物質被覆部の厚さは均一でなくてもよい。正極活物質の表面の少なくとも一部に厚さ１ｎｍ以上の活物質被覆部が存在し、活物質被覆部の厚さの最大値が１００ｎｍ以下であることが好ましい。 As described above, the thickness of the active material coating portion of the positive electrode active material is preferably 1 to 100 nm.
As described above, the thickness of the active material coating portion of the positive electrode active material can be measured by measuring the thickness of the active material coating portion in a transmission electron microscope (TEM) image of the positive electrode active material. The thickness of the active material coating portion present on the surface of the positive electrode active material may not be uniform. It is preferable that an active material coating portion having a thickness of 1 nm or more exists on at least part of the surface of the positive electrode active material, and the maximum thickness of the active material coating portion is 100 nm or less.

正極活物質として用いる粒子（即ち、正極活物質として用いる粉体）の平均粒子径は、例えば０．１～２０．０μｍが好ましく、０．２～１０．０μｍがより好ましい。正極活物質を２種以上用いる場合、それぞれの平均粒子径が上記の範囲内であればよい。
本明細書における正極活物質の平均粒子径は、レーザー回折・散乱法による粒度分布測定器を用いて測定した体積基準のメジアン径である。 The average particle size of the particles used as the positive electrode active material (that is, the powder used as the positive electrode active material) is, for example, preferably 0.1 to 20.0 μm, more preferably 0.2 to 10.0 μm. When two or more kinds of positive electrode active materials are used, each average particle size should be within the above range.
The average particle size of the positive electrode active material in the present specification is a volume-based median size measured using a particle size distribution analyzer based on a laser diffraction/scattering method.

正極活物質層１２に含まれる結着材は有機物であり、例えば、ポリアクリル酸、ポリアクリル酸リチウム、ポリフッ化ビニリデン、ポリフッ化ビニリデン－ヘキサフルオロプロピレン共重合体、スチレンブタジエンゴム、ポリビニルアルコール、ポリビニルアセタール、ポリエチレンオキサイド、ポリエチレングリコール、カルボキシメチルセルロース、ポリアクリルニトリル、ポリイミド等が挙げられる。結着材は１種でもよく、２種以上を併用してもよい。少ない添加量で高い結着性が得られる点で、結着材がポリフッ化ビニリデンを含むことが好ましい。 The binder contained in the positive electrode active material layer 12 is an organic substance, and examples thereof include polyacrylic acid, lithium polyacrylate, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, styrene-butadiene rubber, polyvinyl alcohol, and polyvinylidene. Acetal, polyethylene oxide, polyethylene glycol, carboxymethyl cellulose, polyacrylonitrile, polyimide and the like can be mentioned. One type of binder may be used, or two or more types may be used in combination. It is preferable that the binder contains polyvinylidene fluoride because high binding properties can be obtained with a small addition amount.

正極活物質層１２が結着剤を含有する場合、正極活物質層１２における結着材の含有量は、正極活物質層１２の総質量に対して、０．１～１．０質量％が好ましく、０．３～０．８質量％がより好ましい。正極活物質層１２における結着材の含有量が、上記範囲の下限値以上であると剥離強度の向上効果に優れ、上限値以下であると非水電解質二次電池のインピーダンスの低減効果に優れる。 When the positive electrode active material layer 12 contains a binder, the content of the binder in the positive electrode active material layer 12 is 0.1 to 1.0% by mass with respect to the total mass of the positive electrode active material layer 12. Preferably, 0.3 to 0.8% by mass is more preferable. When the content of the binder in the positive electrode active material layer 12 is at least the lower limit value of the above range, the effect of improving the peel strength is excellent, and when it is at most the upper limit value, the effect of reducing the impedance of the non-aqueous electrolyte secondary battery is excellent. .

正極活物質層１２に含まれる導電助剤としては、例えば、ケッチェンブラック、アセチレンブラック等のカーボンブラック、グラファイト、グラフェン、ハードカーボン、カーボンナノチューブ（ＣＮＴ）等の炭素材料が挙げられる。導電助剤は１種でもよく、２種以上を併用してもよい。
正極活物質層１２における導電助剤の含有量は、例えば、正極活物質の総質量１００質量部に対して、４質量部以下が好ましく、３質量部以下がより好ましく、１質量部以下がさらに好ましく、導電助剤を含まないことが特に好ましい。
正極活物質層１２に導電助剤を配合する場合、導電助剤の下限値は、導電助剤の種類に応じて適宜決定され、例えば、正極活物質層１２の総質量に対して０．１質量％超とされる。
なお、正極活物質層１２が「導電助剤を含まない」とは、実質的に含まないことを意味し、本発明の効果に影響を及ぼさない程度に含むものを排除するものではない。例えば、導電助剤の含有量が正極活物質層１２の総質量に対して０．１質量％以下であれば、実質的に含まれないと判断できる。 Examples of the conductive aid contained in the positive electrode active material layer 12 include carbon black such as ketjen black and acetylene black, and carbon materials such as graphite, graphene, hard carbon, and carbon nanotubes (CNT). One type of conductive aid may be used, or two or more types may be used in combination.
The content of the conductive aid in the positive electrode active material layer 12 is, for example, preferably 4 parts by mass or less, more preferably 3 parts by mass or less, and further 1 part by mass or less with respect to 100 parts by mass of the total mass of the positive electrode active material. Preferably, it is particularly preferable not to contain a conductive aid.
When the positive electrode active material layer 12 is blended with the conductive aid, the lower limit value of the conductive aid is appropriately determined according to the type of the conductive aid. % by mass.
It should be noted that the fact that the positive electrode active material layer 12 "does not contain a conductive aid" means that it does not substantially contain a conductive aid, and does not exclude substances contained to such an extent that the effects of the present invention are not affected. For example, if the content of the conductive aid is 0.1% by mass or less with respect to the total mass of the positive electrode active material layer 12, it can be determined that it is not substantially contained.

［正極集電体］
正極集電体本体１４は金属材料からなる。金属材料としては、銅、アルミニウム、チタン、ニッケル、ステンレス鋼等の導電性を有する金属が例示できる。
正極集電体本体１４の厚みは、例えば８～４０μｍが好ましく、１０～２５μｍがより好ましい。
正極集電体本体１４の厚み及び正極集電体１１の厚みは、マイクロメータを用いて測定できる。測定器の一例としてはミツトヨ社製品名「ＭＤＨ－２５Ｍ」が挙げられる。 [Positive collector]
The positive electrode current collector main body 14 is made of a metal material. Examples of metal materials include conductive metals such as copper, aluminum, titanium, nickel, and stainless steel.
The thickness of the positive electrode current collector main body 14 is, for example, preferably 8 to 40 μm, more preferably 10 to 25 μm.
The thickness of the positive electrode current collector main body 14 and the thickness of the positive electrode current collector 11 can be measured using a micrometer. An example of the measuring instrument is Mitutoyo's product name "MDH-25M".

［集電体被覆層］
集電体被覆層１５は導電材料を含む。
集電体被覆層１５中の導電材料は、炭素を含むことが好ましく、炭素のみからなる導電材料がより好ましい。
集電体被覆層１５は、例えばカーボンブラック等の炭素粒子と結着材を含むコーティング層が好ましい。集電体被覆層１５の結着材は、正極活物質層１２の結着材と同様のものを例示できる。
正極集電体本体１４の表面を集電体被覆層１５で被覆した正極集電体１１は、例えば、導電材料、結着材、及び溶媒を含むスラリーを、グラビア法等の公知の塗工方法を用いて正極集電体本体１４の表面に塗工し、乾燥して溶媒を除去する方法で製造できる。 [Current collector coating layer]
Current collector coating layer 15 includes a conductive material.
The conductive material in the current collector coating layer 15 preferably contains carbon, and more preferably a conductive material consisting only of carbon.
The current collector coating layer 15 is preferably a coating layer containing carbon particles such as carbon black and a binder. The binder for the current collector coating layer 15 can be exemplified by the same binder as the binder for the positive electrode active material layer 12 .
The positive electrode current collector 11 in which the surface of the positive electrode current collector main body 14 is coated with the current collector coating layer 15 is coated with a slurry containing a conductive material, a binder, and a solvent by a known coating method such as a gravure method. can be applied to the surface of the positive electrode current collector body 14 using and dried to remove the solvent.

集電体被覆層１５の厚さは、０．１～４．０μｍが好ましい。
集電体被覆層の厚さは、集電体被覆層の断面の透過電子顕微鏡（ＴＥＭ）像又は走査型電子顕微鏡（ＳＥＭ）像における被覆層の厚さを計測する方法で測定できる。集電体被覆層の厚さは均一でなくてもよい。正極集電体本体１４の表面の少なくとも一部に厚さ０．１μｍ以上の集電体被覆層が存在し、集電体被覆層の厚さの最大値が４．０μｍ以下であることが好ましい。 The thickness of the current collector coating layer 15 is preferably 0.1 to 4.0 μm.
The thickness of the current collector coating layer can be measured by measuring the thickness of the coating layer in a transmission electron microscope (TEM) image or a scanning electron microscope (SEM) image of the cross section of the current collector coating layer. The thickness of the current collector coating layer may not be uniform. A current collector coating layer having a thickness of 0.1 μm or more is present on at least a portion of the surface of the positive electrode current collector body 14, and the maximum thickness of the current collector coating layer is preferably 4.0 μm or less. .

［正極の製造方法］
本実施形態の正極１は、例えば、正極活物質、結着材、及び溶媒を含む正極製造用組成物を、正極集電体１１上に塗工し、乾燥し溶媒を除去して正極活物質層１２を形成する方法で製造できる。正極製造用組成物は導電助剤を含んでもよい。
正極集電体１１上に正極活物質層１２を形成した積層物を、２枚の平板状冶具の間に挟み、厚み方向に均一に加圧する方法で、正極活物質層１２の厚みを調整できる。例えば、ロールプレス機を用いて加圧する方法を使用できる。 [Manufacturing method of positive electrode]
The positive electrode 1 of the present embodiment is produced by, for example, coating a positive electrode production composition containing a positive electrode active material, a binder, and a solvent on the positive electrode current collector 11, drying the solvent, and removing the positive electrode active material. It can be manufactured by the method of forming layer 12 . The composition for positive electrode production may contain a conductive aid.
The thickness of the positive electrode active material layer 12 can be adjusted by a method in which a laminate in which the positive electrode active material layer 12 is formed on the positive electrode current collector 11 is sandwiched between two flat jigs and is evenly pressed in the thickness direction. . For example, a method of applying pressure using a roll press can be used.

正極製造用組成物の溶媒は非水系溶媒が好ましい。例えば、メタノール、エタノール、１－プロパノール、２－プロパノール等のアルコール；Ｎ－メチルピロリドン、Ｎ，Ｎ－ジメチルホルムアミド等の鎖状又は環状アミド；アセトン等のケトンが挙げられる。溶媒は１種でもよく、２種以上を併用してもよい。 A non-aqueous solvent is preferable as the solvent for the positive electrode-manufacturing composition. Examples include alcohols such as methanol, ethanol, 1-propanol and 2-propanol; linear or cyclic amides such as N-methylpyrrolidone and N,N-dimethylformamide; and ketones such as acetone. One type of solvent may be used, or two or more types may be used in combination.

正極活物質を被覆する導電材料及び導電助剤の少なくとも一方が炭素を含む場合、正極活物質層１２の総質量に対して、導電性炭素の含有量は０．５～５．０質量％が好ましく、１．０～３．５質量％がより好ましく、１．０～２．５質量％がさらに好ましい。
正極活物質層１２の総質量に対する導電性炭素の含有量は、正極活物質層１２を剥がして１２０℃環境で真空乾燥した乾燥物（粉体）を測定対象物として、下記≪導電性炭素含有量の測定方法≫で測定できる。測定対象物としての乾燥物である粉体の粒子径については、後述する方法で導電性炭素の含有量の測定が適切に行える限り特に制限はない。
下記≪導電性炭素含有量の測定方法≫で測定した導電性炭素の含有量は、正極活物質を被覆する導電材料中の炭素と、導電助剤中の炭素を含む。結着材中の炭素は含まれない。
正極活物質層１２の総質量に対して、導電性炭素の含有量が上記の範囲内であると、非水電解質二次電池のインピーダンスの低減効果に優れる。 When at least one of the conductive material that coats the positive electrode active material and the conductive aid contains carbon, the content of the conductive carbon is 0.5 to 5.0% by mass with respect to the total mass of the positive electrode active material layer 12. It is preferably 1.0 to 3.5% by mass, even more preferably 1.0 to 2.5% by mass.
The content of conductive carbon with respect to the total mass of the positive electrode active material layer 12 is obtained by using the dried product (powder) obtained by removing the positive electrode active material layer 12 and vacuum-drying it in a 120 ° C. environment as the measurement object, and the following <<contains conductive carbon. Quantity measurement method>>. There is no particular limitation on the particle size of the powder, which is a dry matter to be measured, as long as the content of conductive carbon can be appropriately measured by the method described later.
The content of conductive carbon measured by <<Method for Measuring Content of Conductive Carbon>> below includes carbon in the conductive material covering the positive electrode active material and carbon in the conductive aid. Carbon in the binder is not included.
When the content of the conductive carbon is within the above range with respect to the total mass of the positive electrode active material layer 12, the effect of reducing the impedance of the non-aqueous electrolyte secondary battery is excellent.

前記測定対象物を得る方法としては、例えば、以下の方法を用いることができる。
正極集電体本体１４上に集電体被覆層１５が存在せず、正極集電体本体１４上に正極活物質層１２のみが存在する場合、まず、正極１を任意の大きさに打ち抜き、溶剤（例えば、Ｎ－メチルピロリドン）に浸漬して攪拌する方法で、正極集電体本体１４上に存在する層（粉体）を完全に剥がす。次いで、正極集電体本体１４に粉体が付着していないことを確認し、正極集電体本体１４を溶剤から取り出し、剥がした粉体と溶剤を含む懸濁液（スラリー）を得る。得られた懸濁液を１２０℃で乾燥して溶剤を完全に揮発させ、目的の測定対象物（粉体）を得る。
また、正極集電体本体１４上に集電体被覆層１５及び正極活物質層１２が存在する場合は、正極活物質層１２を構成する粉体のみを剥がし、１２０℃環境で真空乾燥させた乾燥物（粉体）を用いる。例えば、正極活物質層１２の最表面の、深さ数μｍの部分をスパチュラ等で剥がした粉体を１２０℃環境で真空乾燥して測定対象物とすることができる。 As a method for obtaining the measurement object, for example, the following method can be used.
When the current collector coating layer 15 does not exist on the positive electrode current collector main body 14, and only the positive electrode active material layer 12 exists on the positive electrode current collector main body 14, first, the positive electrode 1 is punched into an arbitrary size, The layer (powder) existing on the positive electrode current collector main body 14 is completely peeled off by a method of immersing in a solvent (for example, N-methylpyrrolidone) and stirring. After confirming that no powder adheres to the positive electrode current collector main body 14, the positive electrode current collector main body 14 is removed from the solvent to obtain a suspension (slurry) containing the removed powder and the solvent. The resulting suspension is dried at 120° C. to completely volatilize the solvent to obtain the target measurement object (powder).
Further, when the current collector coating layer 15 and the positive electrode active material layer 12 existed on the positive electrode current collector main body 14, only the powder constituting the positive electrode active material layer 12 was peeled off and vacuum dried in an environment of 120°C. Dried material (powder) is used. For example, the powder obtained by peeling off the outermost surface of the positive electrode active material layer 12 with a depth of several μm with a spatula or the like can be vacuum-dried in an environment of 120° C. and used as an object to be measured.

また、正極１から正極集電体本体１４を除いた残部の質量に対して、導電性炭素の含有量は０．５～５．０質量％が好ましく、１．０～３．５質量％がより好ましく、１．０～２．５質量％がさらに好ましい。
前記残部に対して、導電性炭素の含有量が上記の範囲内であると、非水電解質二次電池のインピーダンスの低減効果に優れる。
正極１が正極集電体本体１４と正極活物質層１２とからなる場合、正極１から正極集電体本体１４を除いた残部の質量は、正極活物質層１２の質量である。
正極１が正極集電体本体１４と集電体被覆層１５と正極活物質層１２とからなる場合、正極１から正極集電体本体１４を除いた残部の質量は、集電体被覆層１５と正極活物質層１２の合計質量である。
正極１から正極集電体本体１４を除いた残部の質量に対する導電性炭素の含有量は、正極集電体本体１４上に存在する層の全量を剥がして１２０℃環境で真空乾燥した乾燥物（粉体）を測定対象物として、下記≪導電性炭素含有量の測定方法≫で測定できる。測定対象物としての乾燥物である粉体の粒子径については、後述する方法で導電性炭素の含有量の測定が適切に行える限り特に制限はない。 In addition, the content of the conductive carbon is preferably 0.5 to 5.0% by mass, more preferably 1.0 to 3.5% by mass, based on the mass of the remainder of the positive electrode 1 excluding the positive electrode current collector body 14. More preferably, 1.0 to 2.5% by mass is even more preferable.
When the content of the conductive carbon is within the above range with respect to the remainder, the effect of reducing the impedance of the non-aqueous electrolyte secondary battery is excellent.
When the positive electrode 1 is composed of the positive electrode current collector main body 14 and the positive electrode active material layer 12 , the mass of the positive electrode 1 excluding the positive electrode current collector main body 14 is the mass of the positive electrode active material layer 12 .
When the positive electrode 1 is composed of the positive electrode current collector main body 14, the current collector coating layer 15, and the positive electrode active material layer 12, the mass of the remainder after removing the positive electrode current collector main body 14 from the positive electrode 1 is the current collector coating layer 15. and the total mass of the positive electrode active material layer 12 .
The content of conductive carbon with respect to the mass of the remainder of the positive electrode 1 excluding the positive electrode current collector main body 14 is obtained by removing the entire amount of the layer existing on the positive electrode current collector main body 14 and vacuum-drying it in a 120 ° C. environment ( Powder) can be measured by the following <<Method for measuring conductive carbon content>>. There are no particular restrictions on the particle size of the powder, which is a dry matter to be measured, as long as the content of conductive carbon can be appropriately measured by the method described later.

≪導電性炭素含有量の測定方法≫
［測定方法Ａ］
測定対象物を均一に混合して試料（質量ｗ１）を量りとり、下記の工程Ａ１、工程Ａ２の手順で熱重量示差熱（ＴＧ－ＤＴＡ）測定を行い、ＴＧ曲線を得る。得られたＴＧ曲線から下記第１の重量減少量Ｍ１（単位：質量％）及び第２の重量減少量Ｍ２（単位：質量％）を求める。Ｍ２からＭ１を減算して導電性炭素の含有量（単位：質量％）を得る。
工程Ａ１：３００ｍＬ／分のアルゴン気流中において、１０℃／分の昇温速度で３０℃から６００℃まで昇温し、６００℃で１０分間保持したときの質量ｗ２から、下記式（ａ１）により第１の重量減少量Ｍ１を求める。
Ｍ１＝（ｗ１－ｗ２）／ｗ１×１００ …（ａ１）
工程Ａ２：前記工程Ａ１の直後に６００℃から１０℃／分の降温速度で降温し、２００℃で１０分間保持した後に、測定ガスをアルゴンから酸素へ完全に置換し、１００ｍＬ／分の酸素気流中において、１０℃／分の昇温速度で２００℃から１０００℃まで昇温し、１０００℃にて１０分間保持したときの質量ｗ３から、下記式（ａ２）により第２の重量減少量Ｍ２（単位：質量％）を求める。
Ｍ２＝（ｗ１－ｗ３）／ｗ１×１００ …（ａ２） <<Method for measuring conductive carbon content>>
[Measurement method A]
The object to be measured is uniformly mixed, a sample (mass w1) is weighed, thermogravimetric differential thermal analysis (TG-DTA) is performed in the following steps A1 and A2, and a TG curve is obtained. From the obtained TG curve, the following first weight reduction amount M1 (unit: mass %) and second weight reduction amount M2 (unit: mass %) are obtained. Subtract M1 from M2 to obtain the content of conductive carbon (unit: % by mass).
Step A1: In an argon stream of 300 mL/min, the temperature is raised from 30° C. to 600° C. at a rate of temperature increase of 10° C./min and held at 600° C. for 10 minutes. A first weight reduction amount M1 is obtained.
M1=(w1-w2)/w1×100 (a1)
Step A2: Immediately after step A1, the temperature is lowered from 600° C. at a rate of 10° C./min, held at 200° C. for 10 minutes, and then the measurement gas is completely replaced from argon to oxygen with an oxygen flow of 100 mL/min. Inside, the temperature is increased from 200 ° C. to 1000 ° C. at a temperature increase rate of 10 ° C./min, and the mass w3 when held at 1000 ° C. for 10 minutes is calculated by the following formula (a2) to obtain the second weight reduction amount M2 ( Unit: % by mass).
M2=(w1-w3)/w1×100 (a2)

［測定方法Ｂ］
測定対象物を均一に混合して試料を０．０００１ｍｇ精秤し、下記の燃焼条件で試料を燃焼し、発生した二酸化炭素をＣＨＮ元素分析装置により定量し、試料に含まれる全炭素量Ｍ３（単位：質量％）を測定する。また、前記測定方法Ａの工程Ａ１の手順で第１の重量減少量Ｍ１を求める。Ｍ３からＭ１を減算して導電性炭素の含有量（単位：質量％）を得る。
［燃焼条件］
燃焼炉：１１５０℃
還元炉：８５０℃
ヘリウム流量：２００ｍＬ／分
酸素流量：２５～３０ｍＬ／分 [Measurement method B]
The object to be measured is uniformly mixed and 0.0001 mg of the sample is precisely weighed, the sample is burned under the following combustion conditions, the carbon dioxide generated is quantified by a CHN elemental analyzer, and the total carbon content M3 ( Unit: % by mass). In addition, the first weight reduction amount M1 is obtained by the procedure of step A1 of the measuring method A described above. Subtract M1 from M3 to obtain the conductive carbon content (unit: % by mass).
[Combustion conditions]
Combustion furnace: 1150°C
Reduction furnace: 850°C
Helium flow rate: 200 mL/min Oxygen flow rate: 25-30 mL/min

［測定方法Ｃ］
上記測定方法Ｂと同様にして、試料に含まれる全炭素量Ｍ３（単位：質量％）を測定する。また、下記の方法で結着材由来の炭素の含有量Ｍ４（単位：質量％）を求める。Ｍ３からＭ４を減算して導電性炭素の含有量（単位：質量％）を得る。
結着材がポリフッ化ビニリデン（ＰＶＤＦ：モノマー（ＣＨ２ＣＦ２）の分子量６４）である場合は、管状式燃焼法による燃焼イオンクロマトグラフィーにより測定されたフッ化物イオン（Ｆ－）の含有量（単位：質量％）、ＰＶＤＦを構成するモノマーのフッ素の原子量（１９）、及びＰＶＤＦを構成する炭素の原子量（１２）から以下の式で計算することができる。
ＰＶＤＦの含有量（単位：質量％）＝フッ化物イオンの含有量（単位：質量％）×６４／３８
ＰＶＤＦ由来の炭素の含有量Ｍ４（単位：質量％）＝フッ化物イオンの含有量（単位：質量％）×１２／１９
結着材がポリフッ化ビニリデンであることは、試料、又は試料をＮ－Ｎジメチルホルムアミド（ＤＭＦ）溶媒により抽出した液体をフーリエ変換赤外スペクトル（ＦＴ－ＩＲ）測定し、Ｃ－Ｆ結合由来の吸収を確認する方法で確かめることができる。同様に１９Ｆ－ＮＭＲ測定でも確かめることができる。
結着材がＰＶＤＦ以外と同定された場合は、その分子量に相当する結着材の含有量（単位：質量％）および炭素の含有量（単位：質量％）を求めることで、結着材由来の炭素量Ｍ４を算出できる。
これらの手法は下記複数の公知文献に記載されている。
東レリサーチセンター Ｔｈｅ ＴＲＣ Ｎｅｗｓ Ｎｏ．１１７ （Ｓｅｐ．２０１３）第３４～３７頁、［２０２１年２月１０日検索］、インターネット＜https://www.toray-research.co.jp/technical-info/trcnews/pdf/TRC117(34-37).pdf＞
東ソー分析センター 技術レポート Ｎｏ．Ｔ１０１９ ２０１７．０９．２０、［２０２１年２月１０日検索］、インターネット＜http://www.tosoh-arc.co.jp/techrepo/files/tarc00522/T1719N.pdf＞ [Measurement method C]
The total carbon content M3 (unit: % by mass) contained in the sample is measured in the same manner as in the measurement method B above. Also, the binder-derived carbon content M4 (unit: % by mass) is determined by the following method. Subtract M4 from M3 to obtain the conductive carbon content (unit: % by mass).
When the binder is polyvinylidene fluoride (PVDF: monomer (CH 2 CF 2 ) molecular weight 64), the content of fluoride ions (F − ) measured by combustion ion chromatography using a tubular combustion method ( Unit: % by mass), the fluorine atomic weight (19) of the monomer constituting PVDF, and the atomic weight (12) of carbon constituting PVDF by the following formula.
PVDF content (unit: mass%) = fluoride ion content (unit: mass%) x 64/38
PVDF-derived carbon content M4 (unit: mass%) = fluoride ion content (unit: mass%) x 12/19
The fact that the binder is polyvinylidene fluoride is confirmed by Fourier transform infrared spectrum (FT-IR) measurement of the sample or the liquid obtained by extracting the sample with N-N dimethylformamide (DMF) solvent, and the C-F bond derived It can be confirmed by a method for confirming absorption. It can also be confirmed by 19 F-NMR measurement.
If the binder is identified to be other than PVDF, the content of the binder (unit: mass %) corresponding to the molecular weight and the content of carbon (unit: mass %) of carbon content M4 can be calculated.
These techniques are described in the following publications.
Toray Research Center The TRC News No. 117 (Sep. 2013) pp. 34-37, [searched on February 10, 2021], Internet <https://www.toray-research.co.jp/technical-info/trcnews/pdf/TRC117(34- 37).pdf＞
Tosoh Analysis Center Technical Report No. T1019 2017.09.20, [searched on February 10, 2021], Internet <http://www.tosoh-arc.co.jp/techrepo/files/tarc00522/T1719N.pdf>

≪導電性炭素の分析方法≫
正極活物質の活物質被覆部を構成する導電性炭素と、導電助剤である導電性炭素は、以下の分析方法で区別できる。
例えば、正極活物質層中の粒子を透過電子顕微鏡電子エネルギー損失分光法（ＴＥＭ－ＥＥＬＳ）により分析し、粒子表面近傍にのみ２９０ｅＶ付近の炭素由来のピークが存在する粒子は正極活物質であり、粒子内部にまで炭素由来のピークが存在する粒子は導電助剤と判定することができる。ここで「粒子表面近傍」とは、粒子表面からの深さが、約１００ｎｍまでの領域を意味し、「粒子内部」とは前記粒子表面近傍よりも内側の領域を意味する。
他の方法としては、正極活物質層中の粒子をラマン分光によりマッピング解析し、炭素由来のＧ－ｂａｎｄとＤ－ｂａｎｄ、及び正極活物質由来の酸化物結晶のピークが同時に観測された粒子は正極活物質であり、Ｇ－ｂａｎｄとＤ－ｂａｎｄのみが観測された粒子は導電助剤と判定することができる。
さらに他の方法としては、広がり抵抗顕微鏡（ＳＳＲＭ：Ｓｃａｎｎｉｎｇ Ｓｐｒｅａｄ Ｒｅｓｉｓｔａｎｃｅ Ｍｉｃｒｏｓｃｏｐｅ）により、正極活物質層の断面を観察し、粒子表面に粒子内部より抵抗が低い部分が存在する場合、抵抗が低い部分は活物質被覆部に存在する導電性炭素であると判定できる。そのような粒子以外に独立して存在し、かつ抵抗が低い部分は導電助剤であると判定することができる。
なお、不純物として考えられる微量な炭素や、製造時に正極活物質の表面から意図せず剥がれた微量な炭素などは、導電助剤と判定しない。
これらの方法を用いて、炭素材料からなる導電助剤が正極活物質層に含まれるか否かを確認することができる。 <<Method for analyzing conductive carbon>>
The conductive carbon that constitutes the active material coating portion of the positive electrode active material and the conductive carbon that is the conductive aid can be distinguished by the following analysis method.
For example, the particles in the positive electrode active material layer are analyzed by transmission electron microscope electron energy loss spectroscopy (TEM-EELS), and particles having a carbon-derived peak near 290 eV only in the vicinity of the particle surface are positive electrode active materials, Particles in which carbon-derived peaks are present even inside the particles can be determined to be conductive aids. Here, "near the particle surface" means a region up to about 100 nm deep from the particle surface, and "inside the particle" means a region inside the vicinity of the particle surface.
As another method, the particles in the positive electrode active material layer are subjected to mapping analysis by Raman spectroscopy. Particles that are positive electrode active materials and in which only the G-band and D-band are observed can be determined as conductive aids.
As yet another method, a scanning spread resistance microscope (SSRM) is used to observe the cross section of the positive electrode active material layer. It can be determined that it is the conductive carbon present in the active material coating portion. It can be determined that a portion that exists independently and has a low resistance other than such particles is the conductive aid.
A small amount of carbon considered as an impurity, a small amount of carbon unintentionally peeled off from the surface of the positive electrode active material during production, and the like are not determined to be conductive aids.
Using these methods, it is possible to confirm whether or not the positive electrode active material layer contains a conductive aid made of a carbon material.

本実施形態において、正極活物質層１２の単位面積あたりの質量は２０～１００ｍｇ／ｃｍ２が好ましく、３０～５０ｍｇ／ｃｍ２がより好ましい。
本明細書における「正極活物質層の単位面積あたりの質量」は、特に断りが無い限り正極集電体の両面に存在する正極活物質層の合計の値である。
正極活物質層１２の単位面積あたりの質量は、例えば以下の測定方法により測定できる。
正極を所定の面積となるように打ち抜いた測定試料の質量を測定し、予め測定した正極集電体１１の質量を差し引いて、正極活物質層の質量を算出する。
正極活物質層の質量（単位：ｍｇ）／測定試料の面積（単位：ｃｍ２）により、正極活物質層１２の単位面積あたりの質量（単位：ｍｇ／ｃｍ２）を求める。
正極活物質層１２の単位面積あたりの質量が上記範囲の下限値以上であると、非水電解質二次電池の重量エネルギー密度の向上効果に優れ、上限値以下であると非水電解質二次電池のインピーダンスの低減効果に優れる。
正極活物質層１２の単位面積あたりの質量は、例えば、正極製造用組成物の塗工量によって調整できる。 In the present embodiment, the mass per unit area of the positive electrode active material layer 12 is preferably 20-100 mg/cm 2 , more preferably 30-50 mg/cm 2 .
The "mass per unit area of the positive electrode active material layer" in this specification is the total value of the positive electrode active material layers present on both sides of the positive electrode current collector unless otherwise specified.
The mass per unit area of the positive electrode active material layer 12 can be measured, for example, by the following measuring method.
The mass of a measurement sample obtained by punching out a positive electrode to have a predetermined area is measured, and the mass of the positive electrode active material layer is calculated by subtracting the mass of the positive electrode current collector 11 measured in advance.
The mass (unit: mg/cm 2 ) per unit area of the positive electrode active material layer 12 is obtained by dividing the mass (unit: mg) of the positive electrode active material layer/the area (unit: cm 2 ) of the measurement sample.
When the mass per unit area of the positive electrode active material layer 12 is at least the lower limit of the above range, the effect of improving the weight energy density of the nonaqueous electrolyte secondary battery is excellent. excellent impedance reduction effect.
The mass per unit area of the positive electrode active material layer 12 can be adjusted, for example, by the coating amount of the positive electrode manufacturing composition.

本実施形態において、正極活物質層１２の粉体抵抗率は１０～１，０００Ω・ｃｍであり、１５～１００Ω・ｃｍが好ましく、２０～５０Ω・ｃｍがより好ましい。
本明細書において、正極活物質層１２の粉体抵抗率は、正極集電体１１上の正極活物質層１２をスパチュラで削って得られるサンプル（粒子群）を、真空乾燥したものを測定対象として粉体抵抗率を測定した値である。
正極活物質層１２の粉体抵抗率が上記範囲の下限値以上であると導電性炭素、結着材が適量であることが想定され、非水電解質二次電池のエネルギー密度向上効果に優れる。上限値以下であると非水電解質二次電池のインピーダンス低減効果に優れる。
前記粉体抵抗率は、例えば、正極活物質の種類、導電助剤の含有量等によって調整できる。正極活物質の種類が同じである場合は、導電助剤の含有量が少ないほど粉体抵抗率は高くなる。 In this embodiment, the powder resistivity of the positive electrode active material layer 12 is 10 to 1,000 Ω·cm, preferably 15 to 100 Ω·cm, more preferably 20 to 50 Ω·cm.
In this specification, the powder resistivity of the positive electrode active material layer 12 is measured by vacuum-drying a sample (particle group) obtained by scraping the positive electrode active material layer 12 on the positive electrode current collector 11 with a spatula. It is a value obtained by measuring the powder resistivity as
When the powder resistivity of the positive electrode active material layer 12 is equal to or higher than the lower limit of the above range, it is assumed that the amount of conductive carbon and binder is appropriate, and the effect of improving the energy density of the non-aqueous electrolyte secondary battery is excellent. When it is equal to or less than the upper limit, the effect of reducing the impedance of the non-aqueous electrolyte secondary battery is excellent.
The powder resistivity can be adjusted by, for example, the type of the positive electrode active material, the content of the conductive aid, and the like. When the type of the positive electrode active material is the same, the powder resistivity increases as the content of the conductive aid decreases.

本実施形態において、正極活物質層１２の剥離強度は１０～１，０００ｍＮ／ｃｍが好ましく、２０～５００ｍＮ／ｃｍがより好ましく、５０～３００ｍＮ／ｃｍがさらに好ましい。
本明細書において、正極活物質層１２の剥離強度は、後述の実施例に記載の測定方法で得られる１８０°剥離強度である。
正極活物質層１２の剥離強度が上記範囲の下限値以上であると、正極活物質層１２を構成する粒子の結着性及び正極集電体１１と正極活物質層１２との密着性に優れる。上限値以下であると導電性炭素、結着材が適量である事が想定され、非水電解質二次電池のエネルギー密度向上効果に優れる。
前記剥離強度は、例えば、結着材の含有量、導電助剤の含有量によって調整できる。結着材の含有量が多いほど剥離強度は高まる。表面積が大きく、結着材を活物質よりも多く必要とする導電助剤の含有量を少なくすることによって、良好な剥離強度を得るために必要な結着材の量を低減できる。 In this embodiment, the peel strength of the positive electrode active material layer 12 is preferably 10 to 1,000 mN/cm, more preferably 20 to 500 mN/cm, even more preferably 50 to 300 mN/cm.
In the present specification, the peel strength of the positive electrode active material layer 12 is the 180° peel strength obtained by the measurement method described in Examples below.
When the peel strength of the positive electrode active material layer 12 is at least the lower limit of the above range, the adhesion of the particles constituting the positive electrode active material layer 12 and the adhesion between the positive electrode current collector 11 and the positive electrode active material layer 12 are excellent. . If it is equal to or less than the upper limit, it is assumed that the amounts of the conductive carbon and the binder are appropriate, and the effect of improving the energy density of the non-aqueous electrolyte secondary battery is excellent.
The peel strength can be adjusted by, for example, the content of the binder and the content of the conductive aid. The peel strength increases as the content of the binder increases. By reducing the content of the conductive aid, which has a large surface area and requires more binder than the active material, the amount of binder required to obtain good peel strength can be reduced.

＜非水電解質二次電池＞
図２に示す本実施形態の非水電解質二次電池１０は、本実施形態の非水電解質二次電池用正極１と、負極３と、非水電解質とを備える。さらにセパレータ２を備えてもよい。図中符号５は外装体である。
本実施形態において、正極１は、板状の正極集電体１１と、その両面上に設けられた正極活物質層１２と有する。正極活物質層１２は正極集電体１１の表面の一部に存在する。正極集電体１１の表面の縁部は、正極活物質層１２が存在しない正極集電体露出部１３である。正極集電体露出部１３の任意の箇所に、図示しない端子用タブが電気的に接続する。
負極３は、板状の負極集電体３１と、その両面上に設けられた負極活物質層３２とを有する。負極活物質層３２は負極集電体３１の表面の一部に存在する。負極集電体３１の表面の縁部は、負極活物質層３２が存在しない負極集電体露出部３３である。負極集電体露出部３３の任意の箇所に、図示しない端子用タブが電気的に接続する。
正極１、負極３およびセパレータ２の形状は特に限定されない。例えば平面視矩形状でもよい。
本実施形態の非水電解質二次電池１０は、例えば、正極１と負極３を、セパレータ２を介して交互に積層した電極積層体を作製し、電極積層体をアルミラミネート袋等の外装体（筐体）５に封入し、非水電解質（図示せず）を注入して密閉する方法で製造できる。
図２では、代表的に、負極／セパレータ／正極／セパレータ／負極の順に積層した構造を示しているが、電極の数は適宜変更できる。正極１は１枚以上あればよく、得ようとする電池容量に応じて任意の数の正極１を用いることができる。負極３及びセパレータ２は、正極１の数より１枚多く用い、最外層が負極３となるように積層する。 <Non-aqueous electrolyte secondary battery>
A non-aqueous electrolyte secondary battery 10 of the present embodiment shown in FIG. 2 includes the positive electrode 1 for non-aqueous electrolyte secondary batteries of the present embodiment, a negative electrode 3, and a non-aqueous electrolyte. Further, a separator 2 may be provided. Reference numeral 5 in the figure is an exterior body.
In this embodiment, the positive electrode 1 has a plate-like positive electrode current collector 11 and positive electrode active material layers 12 provided on both sides thereof. The positive electrode active material layer 12 exists on part of the surface of the positive electrode current collector 11 . An edge portion of the surface of the positive electrode current collector 11 is a positive electrode current collector exposed portion 13 where the positive electrode active material layer 12 does not exist. A terminal tab (not shown) is electrically connected to an arbitrary portion of the positive electrode current collector exposed portion 13 .
The negative electrode 3 has a plate-like negative electrode current collector 31 and negative electrode active material layers 32 provided on both sides thereof. The negative electrode active material layer 32 exists on part of the surface of the negative electrode current collector 31 . An edge portion of the surface of the negative electrode current collector 31 is a negative electrode current collector exposed portion 33 where the negative electrode active material layer 32 does not exist. A terminal tab (not shown) is electrically connected to an arbitrary portion of the negative electrode current collector exposed portion 33 .
The shapes of the positive electrode 1, the negative electrode 3 and the separator 2 are not particularly limited. For example, it may be rectangular in plan view.
The non-aqueous electrolyte secondary battery 10 of the present embodiment is produced, for example, by fabricating an electrode laminate in which the positive electrode 1 and the negative electrode 3 are alternately laminated with the separator 2 interposed therebetween, and the electrode laminate is packaged in an outer package such as an aluminum laminate bag ( It can be manufactured by a method of enclosing in a housing 5, injecting a non-aqueous electrolyte (not shown), and sealing.
FIG. 2 typically shows a structure in which negative electrodes/separators/positive electrodes/separators/negative electrodes are laminated in this order, but the number of electrodes can be changed as appropriate. One or more positive electrodes 1 are sufficient, and any number of positive electrodes 1 can be used according to the battery capacity to be obtained. One more negative electrode 3 and separator 2 than the number of positive electrodes 1 are used, and they are laminated so that the negative electrode 3 is the outermost layer.

［負極］
負極活物質層３２は負極活物質を含む。さらに結着材を含んでもよい。さらに導電助剤を含んでもよい。負極活物質の形状は、粒子状が好ましい。
負極３は、例えば、負極活物質、結着材、及び溶媒を含む負極製造用組成物を調製し、これを負極集電体３１上に塗工し、乾燥し溶媒を除去して負極活物質層３２を形成する方法で製造できる。負極製造用組成物は導電助剤を含んでもよい。 [Negative electrode]
The negative electrode active material layer 32 contains a negative electrode active material. Furthermore, a binding material may be included. Further, it may contain a conductive aid. The shape of the negative electrode active material is preferably particulate.
For the negative electrode 3, for example, a negative electrode manufacturing composition containing a negative electrode active material, a binder, and a solvent is prepared, coated on the negative electrode current collector 31, and dried to remove the solvent to obtain the negative electrode active material. It can be manufactured by any method that forms layer 32 . The negative electrode production composition may contain a conductive aid.

負極活物質及び導電助剤としては、例えば、ケッチェンブラック、アセチレンブラック等のカーボンブラック、グラファイト、グラフェン、ハードカーボン、カーボンナノチューブ（ＣＮＴ）等の炭素材料が挙げられる。負極活物質及び導電助剤は、それぞれ１種でもよく２種以上を併用してもよい。 Examples of the negative electrode active material and conductive aid include carbon black such as ketjen black and acetylene black, and carbon materials such as graphite, graphene, hard carbon, and carbon nanotube (CNT). Each of the negative electrode active material and the conductive aid may be used alone or in combination of two or more.

負極集電体３１の材料、負極製造用組成物中の結着材、溶媒としては、上記した正極集電体１１の材料、正極製造用組成物中の結着材、溶媒と同様のものを例示できる。負極製造用組成物中の結着材、溶媒は、それぞれ１種でもよく２種以上を併用してもよい。 As the material of the negative electrode current collector 31 and the binder and solvent in the composition for manufacturing the negative electrode, the same materials as the material of the positive electrode current collector 11 and the binder and solvent in the composition for manufacturing the positive electrode are used. I can give an example. The binder and the solvent in the negative electrode-producing composition may be used alone or in combination of two or more.

負極活物質層３２の総質量に対して、負極活物質及び導電助剤の合計の含有量は８０．０～９９．９質量％が好ましく、８５．０～９８．０質量％がより好ましい。 The total content of the negative electrode active material and the conductive aid is preferably 80.0 to 99.9 mass %, more preferably 85.0 to 98.0 mass %, relative to the total mass of the negative electrode active material layer 32 .

［セパレータ］
セパレータ２を負極３と正極１との間に配置して短絡等を防止する。セパレータ２は、後述する非水電解質を保持してもよい。
セパレータ２としては、特に限定されず、多孔性の高分子膜、不織布、ガラスファイバー等が例示できる。
セパレータ２の一方又は両方の表面上に絶縁層を設けてもよい。絶縁層は、絶縁性微粒子を絶縁層用結着材で結着した多孔質構造を有する層が好ましい。 [Separator]
A separator 2 is arranged between the negative electrode 3 and the positive electrode 1 to prevent short circuit or the like. The separator 2 may hold a non-aqueous electrolyte, which will be described later.
The separator 2 is not particularly limited, and can be exemplified by porous polymer membranes, non-woven fabrics, glass fibers, and the like.
An insulating layer may be provided on one or both surfaces of the separator 2 . The insulating layer is preferably a layer having a porous structure in which insulating fine particles are bound with an insulating layer binder.

セパレータ２は、各種可塑剤、酸化防止剤、難燃剤を含んでもよい。
酸化防止剤としては、ヒンダードフェノール系酸化防止剤、モノフェノール系酸化防止剤、ビスフェノール系酸化防止剤、ポリフェノール系酸化防止剤等のフェノール系酸化防止剤；ヒンダードアミン系酸化防止剤；リン系酸化防止剤；イオウ系酸化防止剤；ベンゾトリアゾール系酸化防止剤；ベンゾフェノン系酸化防止剤；トリアジン系酸化防止剤；サルチル酸エステル系酸化防止剤等が例示できる。フェノール系酸化防止剤、リン系酸化防止剤が好ましい。 The separator 2 may contain various plasticizers, antioxidants and flame retardants.
Antioxidants include phenolic antioxidants such as hindered phenolic antioxidants, monophenolic antioxidants, bisphenolic antioxidants, and polyphenolic antioxidants; hindered amine antioxidants; phosphorus antioxidants. benzotriazole-based antioxidants; benzophenone-based antioxidants; triazine-based antioxidants; salicylic acid ester-based antioxidants, and the like. Phenolic antioxidants and phosphorus antioxidants are preferred.

［非水電解質］
非水電解質は正極１と負極３との間を満たす。例えば、リチウムイオン二次電池、電気二重層キャパシタ等において公知の非水電解質を使用できる。
非水電解質として、有機溶媒に電解質塩を溶解した非水電解液が好ましい。 [Non-aqueous electrolyte]
A non-aqueous electrolyte fills between the positive electrode 1 and the negative electrode 3 . For example, known nonaqueous electrolytes can be used in lithium ion secondary batteries, electric double layer capacitors and the like.
As the non-aqueous electrolyte, a non-aqueous electrolytic solution obtained by dissolving an electrolyte salt in an organic solvent is preferable.

有機溶媒は、高電圧に対する耐性を有するものが好ましい。例えば、エチレンカーボネート、プロピレンカーボネート、ジメチルカーボネート、ジエチルカーボネート、エチルメチルカーボネート、γ－ブチロラクトン、スルホラン、ジメチルスルホキシド、アセトニトリル、ジメチルホルムアミド、ジメチルアセトアミド、１，２－ジメトキシエタン、１，２－ジエトキシエタン、テトロヒドラフラン、２－メチルテトラヒドロフラン、ジオキソラン、メチルアセテート等の極性溶媒、又はこれら極性溶媒の２種類以上の混合物が挙げられる。 The organic solvent preferably has resistance to high voltage. For example, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, sulfolane, dimethyl sulfoxide, acetonitrile, dimethylformamide, dimethylacetamide, 1,2-dimethoxyethane, 1,2-diethoxyethane, Polar solvents such as tetrahydrafuran, 2-methyltetrahydrofuran, dioxolane, methyl acetate, or mixtures of two or more of these polar solvents are included.

電解質塩は、特に限定されず、例えばＬｉＣｌＯ４、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＡｓＦ６、ＬｉＣＦ６、ＬｉＣＦ３ＣＯ２、ＬｉＰＦ６ＳＯ３、ＬｉＮ（ＳＯ２Ｆ）２、ＬｉＮ（ＳＯ２ＣＦ３）２、Ｌｉ（ＳＯ２ＣＦ２ＣＦ３）２、ＬｉＮ（ＣＯＣＦ３）２、ＬｉＮ（ＣＯＣＦ２ＣＦ３）２等のリチウムを含む塩、又はこれら塩の２種以上の混合物が挙げられる。 The electrolyte salt is not particularly limited, and examples thereof include LiClO 4 , LiPF 6 , LiBF 4 , LiAsF 6 , LiCF 6 , LiCF 3 CO 2 , LiPF 6 SO 3 , LiN(SO 2 F) 2 and LiN(SO 2 CF 3 ). 2 , Li( SO2CF2CF3 ) 2 , LiN( COCF3 ) 2 , LiN( COCF2CF3 ) 2 , or a mixture of two or more of these salts.

本実施形態の非水電解質二次電池は、産業用、民生用、自動車用、住宅用等、各種用途のリチウムイオン二次電池として使用できる。
本実施形態の非水電解質二次電池の使用形態は特に限定されない。例えば、複数個の非水電解質二次電池を直列又は並列に接続して構成した電池モジュール、電気的に接続した複数個の電池モジュールと電池制御システムとを備える電池システム等に用いることができる。
電池システムの例としては、電池パック、定置用蓄電池システム、自動車の動力用蓄電池システム、自動車の補機用蓄電池システム、非常電源用蓄電池システム等が挙げられる。 The non-aqueous electrolyte secondary battery of the present embodiment can be used as a lithium ion secondary battery for various uses such as industrial use, consumer use, automobile use, and residential use.
The mode of use of the non-aqueous electrolyte secondary battery of this embodiment is not particularly limited. For example, it can be used for a battery module configured by connecting a plurality of non-aqueous electrolyte secondary batteries in series or in parallel, a battery system including a plurality of electrically connected battery modules and a battery control system, and the like.
Examples of battery systems include battery packs, stationary storage battery systems, automotive power storage battery systems, automotive auxiliary equipment storage battery systems, and emergency power supply storage battery systems.

本実施形態によれば、重量エネルギー密度に優れた非水電解質二次電池を得ることができる。例えば重量エネルギー密度１２０Ｗｈ／ｋｇ以上、好ましくは１３０Ｗｈ／ｋｇ以上、より好ましくは１４０Ｗｈ／ｋｇ以上を達成できる。 According to this embodiment, a non-aqueous electrolyte secondary battery having excellent weight energy density can be obtained. For example, a weight energy density of 120 Wh/kg or more, preferably 130 Wh/kg or more, more preferably 140 Wh/kg or more can be achieved.

また、本発明においては、上述した第１の実施形態、第２の実施態様及び第３の実施態様の特徴を、適宜、組み合わせることもできる。具体的には、本発明は更に以下の態様を有する。
［Ｄ１］正極集電体と、前記正極集電体上に存在する正極活物質層を有し、下記（Ｄ１－１）、（Ｄ１－２）及び（Ｄ１－３）の少なくとも１つを満たす、非水電解質二次電池用正極：
（Ｄ１－１）前記正極活物質層が正極活物質粒子を含み、前記正極活物質層の拡がり抵抗値分布において、抵抗値４．０～１２．５（ｌｏｇΩ）の頻度合計を１００％とするとき、抵抗値４．０～６．０（ｌｏｇΩ）の頻度合計が０．０～５．０％であり、であり、好ましくは０．０～４．０％であり、より好ましくは０．０～３．０％であり、さらに好ましくは０．０～２．０％である；
（Ｄ１－２）前記正極活物質層が正極活物質及び導電性炭素材料を含み、前記正極活物質層の総質量に対して、抵抗率が０．１０Ω・ｃｍ以下である低抵抗導電性炭素材料の含有量が０．５質量％以下であり、好ましくは０．３質量％以下であり、より好ましくは０．２質量％以下であり、さらに好ましくは０．１質量％以下である；及び
（Ｄ１－３）前記正極活物質層が正極活物質を含み、前記正極活物質の表面の少なくとも一部に、導電材料を含む活物質被覆部が存在し、前記正極活物質層の粉体抵抗率が１０～１，０００Ω・ｃｍであり、１５～１００Ω・ｃｍであることが好ましく、２０～５０Ω・ｃｍであることがより好ましい。
［Ｄ２］ 前記拡がり抵抗値分布において、抵抗値４．０～６．０（ｌｏｇΩ）の平均頻度（平均頻度Ａ、％）より、抵抗値６．０～９．０（ｌｏｇΩ）の平均頻度（平均頻度Ｂ、％）が大きく（即ち、Ａ＜Ｂ）、平均頻度Ａと平均頻度Ｂとの差（Ｂ－Ａ）は０％超が好ましく、０．０５％以上がより好ましく、０．２０％以上がさらに好ましい、［Ｄ１］の非水電解質二次電池用正極。
［Ｄ３］ 前記正極活物質層が導電助剤を含み、前記導電助剤は、グラファイト、グラフェン、ハードカーボン、ケッチェンブラック、アセチレンブラック、及びカーボンナノチューブ（ＣＮＴ）からなる群より選ばれる少なくとも１種の炭素材料であることが好ましく、正極活物質層における導電助剤の含有量は、正極活物質の総質量１００質量部に対して、４質量部以下が好ましく、３質量部以下がより好ましく、１質量部以下がさらに好ましい、［Ｄ１］又は［Ｄ２］の非水電解質二次電池用正極。
［Ｄ４］ 前記正極活物質粒子の表面の少なくとも一部に、導電材料を含む活物質被覆部が存在する、［Ｄ３］の非水電解質二次電池用正極。
［Ｄ５］ 前記正極活物質層が導電助剤を含まず、前記正極活物質粒子の表面の少なくとも一部に、導電材料を含む活物質被覆部が存在する、［Ｄ１］又は［Ｄ２］の非水電解質二次電池用正極。
［Ｄ６］ 前記正極活物質層が導電性炭素を含み、前記正極活物質層の総質量に対して前記導電性炭素の含有量が０．５質量％以上３．０質量％未満であり、１．０～２．８質量％がより好ましく、１．３～２．５質量％がさらに好ましい、［Ｄ３］～［Ｄ５］のいずれかの非水電解質二次電池用正極。
［Ｄ７］ 前記正極活物質粒子が、一般式ＬｉＦｅｘＭ（１－ｘ）ＰＯ４（式中、０≦ｘ≦１、ＭはＣｏ、Ｎｉ、Ｍｎ、Ａｌ、Ｔｉ又はＺｒである。）で表される化合物を含み、前記化合物はＬｉＦｅＰＯ４で表されるリン酸鉄リチウムであることが好ましい、［Ｄ１］～［Ｄ６］のいずれかの非水電解質二次電池用正極。
［Ｄ８］ 前記集電体の、前記正極活物質層側の表面の少なくとも一部に、導電材料を含む集電体被覆層が存在し、前記表面において集電体被覆層が存在する部分の面積が、前記表面の総面積に対して、好ましくは１０％～１００％、より好ましくは３０％～１００％、さらに好ましくは５０％～１００％である、［Ｄ１］～［Ｄ７］のいずれかの非水電解質二次電池用正極。
［Ｄ９］ 前記正極活物質層の総質量に対して、抵抗率が０．０２Ω・ｃｍ以下である低抵抗導電性炭素材料の含有量が０．５質量％以下であり、より好ましくは０．３質量％以下であり、さらに好ましくは０．２質量％以下であり、特に好ましくは０．１質量％以下である、［Ｄ１］～［Ｄ８］のいずれかの非水電解質二次電池用正極。
［Ｄ１０］ 前記正極活物質層が、前記正極活物質からなる粒子本体と、前記粒子本体の表面の少なくとも一部に存在する活物質被覆部を含み、前記導電性炭素材料の少なくとも一部が前記活物質被覆部であり、前記活物質被覆部の抵抗率が０．１５Ω・ｃｍ以上であり、０．１５Ω・ｃｍ～１．０Ω・ｃｍであることが好ましく、０．２０Ω・ｃｍ～０．５Ω・ｃｍであることがより好ましく、０．２５Ω・ｃｍ～０．４Ω・ｃｍであることがさらに好ましい、［Ｄ１］～［Ｄ９］のいずれかの非水電解質二次電池用正極。
［Ｄ１１］前記正極活物質層の総質量に対して、前記活物質被覆部の含有量が０．９質量％以上であり、１．０質量％以上であることが好ましく、１．１質量％以上であることがより好ましい、［Ｄ１０］の非水電解質二次電池用正極。
［Ｄ１２］ 前記正極活物質層が導電助剤を含み、前記導電性炭素材料の少なくとも一部が前記導電助剤であって、前記導電助剤は、グラファイト、グラフェン、ハードカーボン、ケッチェンブラック、アセチレンブラック、及びカーボンナノチューブ（ＣＮＴ）からなる群より選ばれる少なくとも１種の炭素材料であることが好ましく、正極活物質層における導電助剤の含有量は、正極活物質層の総質量に対して、４質量％以下が好ましく、３質量％以下がより好ましく、１質量％以下がさらに好ましい、［Ｄ１］～［Ｄ１１］のいずれかの非水電解質二次電池用正極。
［Ｄ１３］ 前記正極活物質層が結着材を含み、前記正極活物質層の総質量に対して、結着材の含有量が０．１～１．０質量％であり、０．３～０．８質量％であることが好ましい、［Ｄ１］～［Ｄ１２］の非水電解質二次電池用正極。
［Ｄ１４］ 前記結着材がポリフッ化ビニリデンを含む、［Ｄ１３］の非水電解質二次電池用正極。
［Ｄ１５］ 前記正極活物質層の剥離強度が１０～１，０００ｍＮ／ｃｍであり、２０～５００ｍＮ／ｃｍであることが好ましく、５０～３００ｍＮ／ｃｍであることがさらに好ましい、［Ｄ１］～［Ｄ１４］のいずれかの非水電解質二次電池用正極。
［Ｄ１６］ 前記正極集電体の両面に前記正極活物質層が存在し、前記両面の正極活物質層の合計の単位面積あたりの質量が２０～１００ｍｇ／ｃｍ２であり、３０～５０ｍｇ／ｃｍ２であることがより好ましい、［Ｄ１］～［Ｄ１５］のいずれかの非水電解質二次電池用正極。
［Ｄ１７］ 前記正極集電体の、前記正極活物質層側の表面に集電体被覆層が存在する、［Ｄ１］～［Ｄ１６］のいずれかの非水電解質二次電池用正極。
［Ｄ１８］ 前記集電体被覆層が炭素を含み、炭素粒子（カーボンブラック等）と結着材を含むことが好ましい、［Ｄ１７］の非水電解質二次電池用正極。
［Ｄ１９］ 前記導電材料が炭素を含み、炭素のみからなることが好ましく、活物質被覆部を有する正極活物質の総質量に対して、前記導電材料の含有量は０．１～３．０質量％が好ましく、０．５～１．５質量％がより好ましく、０．７～１．３質量％がさらに好ましい、［Ｄ１］～［Ｄ１８］のいずれかの非水電解質二次電池用正極。
［Ｄ２０］ 前記正極活物質層が導電助剤を含まない、［Ｄ１］、［Ｄ２］、［Ｄ７］～［Ｄ１１］、及び［Ｄ１３］～［Ｄ１９］のいずれかの非水電解質二次電池用正極。
［Ｄ２１］ 前記［Ｄ１］～［Ｄ２０］のいずれかの非水電解質二次電池用正極、負極、及び前記非水電解質二次電池用正極と負極との間に存在する非水電解質を備える、非水電解質二次電池。
［Ｄ２２］ 重量エネルギー密度が１２０Ｗｈ／ｋｇ以上であり、好ましくは１３０Ｗｈ／ｋｇ以上であり、より好ましくは１４０Ｗｈ／ｋｇ以上である、［Ｄ２１］の非水電解質二次電池。
［Ｄ２３］ ［Ｄ２１］又は［Ｄ２２］の非水電解質二次電池の複数個を備える、電池モジュール又は電池システム。 Moreover, in the present invention, the features of the above-described first embodiment, second embodiment, and third embodiment can be combined as appropriate. Specifically, the present invention further has the following aspects.
[D1] Having a positive electrode current collector and a positive electrode active material layer present on the positive electrode current collector, satisfying at least one of the following (D1-1), (D1-2) and (D1-3) , Positive electrode for non-aqueous electrolyte secondary battery:
(D1-1) The positive electrode active material layer contains positive electrode active material particles, and the total frequency of resistance values 4.0 to 12.5 (log Ω) in the spreading resistance value distribution of the positive electrode active material layer is 100%. When the total frequency of resistance values 4.0 to 6.0 (log Ω) is 0.0 to 5.0%, preferably 0.0 to 4.0%, more preferably 0.0% to 5.0%. 0 to 3.0%, more preferably 0.0 to 2.0%;
(D1-2) Low-resistance conductive carbon in which the positive electrode active material layer contains a positive electrode active material and a conductive carbon material and has a resistivity of 0.10 Ω·cm or less with respect to the total mass of the positive electrode active material layer. the material content is 0.5% by mass or less, preferably 0.3% by mass or less, more preferably 0.2% by mass or less, and even more preferably 0.1% by mass or less; and (D1-3) The positive electrode active material layer contains a positive electrode active material, an active material coating portion containing a conductive material is present on at least a part of the surface of the positive electrode active material, and the powder resistance of the positive electrode active material layer The modulus is 10 to 1,000 Ω·cm, preferably 15 to 100 Ω·cm, more preferably 20 to 50 Ω·cm.
[D2] In the spreading resistance value distribution, the average frequency of resistance values 6.0 to 9.0 (log Ω) ( The average frequency B, %) is large (that is, A < B), and the difference (BA) between the average frequency A and the average frequency B is preferably more than 0%, more preferably 0.05% or more, and 0.20 % or more is more preferable, the positive electrode for non-aqueous electrolyte secondary batteries of [D1].
[D3] The positive electrode active material layer contains a conductive aid, and the conductive aid is at least one selected from the group consisting of graphite, graphene, hard carbon, ketjen black, acetylene black, and carbon nanotubes (CNT). The content of the conductive aid in the positive electrode active material layer is preferably 4 parts by mass or less, more preferably 3 parts by mass or less, with respect to 100 parts by mass of the total mass of the positive electrode active material, The positive electrode for a non-aqueous electrolyte secondary battery of [D1] or [D2], which is more preferably 1 part by mass or less.
[D4] The positive electrode for a non-aqueous electrolyte secondary battery according to [D3], wherein an active material coating containing a conductive material is present on at least part of the surface of the positive electrode active material particles.
[D5] The non of [D1] or [D2], wherein the positive electrode active material layer does not contain a conductive aid, and an active material coating portion containing a conductive material is present on at least part of the surface of the positive electrode active material particles. Positive electrode for water electrolyte secondary battery.
[D6] the positive electrode active material layer contains conductive carbon, and the content of the conductive carbon is 0.5% by mass or more and less than 3.0% by mass with respect to the total mass of the positive electrode active material layer; The positive electrode for a non-aqueous electrolyte secondary battery according to any one of [D3] to [D5], which is more preferably 0 to 2.8% by mass, further preferably 1.3 to 2.5% by mass.
[D7] The positive electrode active material particles have the general formula LiFe x M (1-x) PO 4 (where 0≦x≦1 and M is Co, Ni, Mn, Al, Ti or Zr). The positive electrode for a non-aqueous electrolyte secondary battery according to any one of [D1] to [D6], wherein the compound is preferably lithium iron phosphate represented by LiFePO 4 .
[D8] A current collector coating layer containing a conductive material is present on at least part of the surface of the current collector on the positive electrode active material layer side, and the area of the portion of the surface where the current collector coating layer is present is preferably 10% to 100%, more preferably 30% to 100%, and even more preferably 50% to 100% of the total area of the surface [D1] to [D7]. Positive electrode for non-aqueous electrolyte secondary battery.
[D9] The content of the low-resistance conductive carbon material having a resistivity of 0.02 Ω·cm or less is 0.5% by mass or less, more preferably 0.5% by mass or less, relative to the total mass of the positive electrode active material layer. The positive electrode for a non-aqueous electrolyte secondary battery according to any one of [D1] to [D8], which is 3% by mass or less, more preferably 0.2% by mass or less, and particularly preferably 0.1% by mass or less. .
[D10] The positive electrode active material layer includes a particle body made of the positive electrode active material and an active material coating portion present on at least part of the surface of the particle body, and at least part of the conductive carbon material is the The active material coating portion has a resistivity of 0.15 Ω·cm or more, preferably 0.15 Ω·cm to 1.0 Ω·cm, and 0.20 Ω·cm to 0.20 Ω·cm. The positive electrode for a non-aqueous electrolyte secondary battery according to any one of [D1] to [D9], which is more preferably 5 Ω·cm, further preferably 0.25 Ω·cm to 0.4 Ω·cm.
[D11] The content of the active material coating portion is 0.9% by mass or more, preferably 1.0% by mass or more, and 1.1% by mass with respect to the total mass of the positive electrode active material layer. The positive electrode for a non-aqueous electrolyte secondary battery of [D10], which is more preferably the above.
[D12] The positive electrode active material layer contains a conductive aid, and at least part of the conductive carbon material is the conductive aid, and the conductive aid is graphite, graphene, hard carbon, ketjen black, It is preferably at least one carbon material selected from the group consisting of acetylene black and carbon nanotubes (CNT), and the content of the conductive aid in the positive electrode active material layer is relative to the total mass of the positive electrode active material layer. , preferably 4% by mass or less, more preferably 3% by mass or less, and further preferably 1% by mass or less, the positive electrode for a non-aqueous electrolyte secondary battery according to any one of [D1] to [D11].
[D13] The positive electrode active material layer contains a binder, and the content of the binder is 0.1 to 1.0% by mass and 0.3 to 0.3% by mass with respect to the total mass of the positive electrode active material layer. The positive electrode for non-aqueous electrolyte secondary batteries of [D1] to [D12] preferably has a content of 0.8% by mass.
[D14] The positive electrode for a non-aqueous electrolyte secondary battery of [D13], wherein the binder contains polyvinylidene fluoride.
[D15] The positive electrode active material layer has a peel strength of 10 to 1,000 mN/cm, preferably 20 to 500 mN/cm, more preferably 50 to 300 mN/cm. D14].
[D16] The positive electrode active material layers are present on both sides of the positive electrode current collector, and the total mass per unit area of the positive electrode active material layers on both sides is 20 to 100 mg/cm 2 , and the total mass per unit area is 30 to 50 mg/cm. 2 , the positive electrode for a non-aqueous electrolyte secondary battery according to any one of [D1] to [D15].
[D17] The positive electrode for a nonaqueous electrolyte secondary battery according to any one of [D1] to [D16], wherein a current collector coating layer is present on the surface of the positive electrode current collector on the positive electrode active material layer side.
[D18] The positive electrode for a non-aqueous electrolyte secondary battery of [D17], wherein the current collector coating layer contains carbon, and preferably contains carbon particles (such as carbon black) and a binder.
[D19] It is preferable that the conductive material contains carbon and consists only of carbon, and the content of the conductive material is 0.1 to 3.0 mass relative to the total mass of the positive electrode active material having the active material coating. %, more preferably 0.5 to 1.5% by mass, and even more preferably 0.7 to 1.3% by mass, the positive electrode for a non-aqueous electrolyte secondary battery according to any one of [D1] to [D18].
[D20] The nonaqueous electrolyte secondary battery of any one of [D1], [D2], [D7] to [D11], and [D13] to [D19], wherein the positive electrode active material layer does not contain a conductive aid. positive electrode.
[D21] A positive electrode for a non-aqueous electrolyte secondary battery according to any one of [D1] to [D20], a negative electrode, and a non-aqueous electrolyte present between the positive electrode and the negative electrode for a non-aqueous electrolyte secondary battery, Non-aqueous electrolyte secondary battery.
[D22] The nonaqueous electrolyte secondary battery of [D21], which has a weight energy density of 120 Wh/kg or more, preferably 130 Wh/kg or more, and more preferably 140 Wh/kg or more.
[D23] A battery module or battery system comprising a plurality of non-aqueous electrolyte secondary batteries of [D21] or [D22].

以下に実施例を用いて本発明をさらに詳しく説明するが、本発明はこれら実施例に限定されるものではない。 EXAMPLES The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

＜測定方法＞
［拡がり抵抗値分布］
正極活物質層の厚さ方向に平行な断面を測定対象とし、ＳＳＲＭを用い、下記の条件で拡がり抵抗値分布を測定した。
（使用装置）Ｂｒｕｋｅｒ社製、製品名：ＮａｎｏＳｃｏｐｅＶ ＤｉｍｅｎｓｉｏｎＩｃｏｎ、Ｇｌｏｖｅｂｏｘ。
（試料の調製）正極シートから切り出した試験片をエポキシ樹脂で包埋した後、ブロードイオンビーム加工により切断して断面を作製し、不活性雰囲気下で測定装置内に導入した。
（測定条件）
走査モード：コンタクトモードと拡がり抵抗の同時測定。
探針（Ｔｉｐ）：ダイヤモンドコートシリコンカンチレバー（ＤＤＥＳＰ １０）。
測定環境：室温、高純度Ａｒガス雰囲気中（Ｈ２Ｏ＝０．１ｐｐｍ、Ｏ２＝０．１ｐｐｍ）。
印加電圧：ＤＣバイアス電圧＝＋２．０Ｖ。
スキャンサイズ：６０μｍ×６０μｍ。
測定点の数（データ点数）：１０２４×１０２４。 <Measurement method>
[Spreading resistance distribution]
Using a cross section parallel to the thickness direction of the positive electrode active material layer as a measurement target, the spreading resistance value distribution was measured using SSRM under the following conditions.
(Apparatus used) Bruker, product name: NanoScopeV Dimension Icon, Glovebox.
(Preparation of Sample) A test piece cut out from the positive electrode sheet was embedded in an epoxy resin, cut by broad ion beam processing to prepare a cross section, and introduced into a measuring apparatus under an inert atmosphere.
(Measurement condition)
Scan mode: Simultaneous measurement of contact mode and spreading resistance.
Tip: Diamond coated silicon cantilever (DDESP 10).
Measurement environment: room temperature, high-purity Ar gas atmosphere (H 2 O=0.1 ppm, O 2 =0.1 ppm).
Applied voltage: DC bias voltage = +2.0V.
Scan size: 60 μm×60 μm.
Number of measurement points (number of data points): 1024×1024.

［体積密度の測定方法］
マイクロゲージを用いて正極シートの厚み及び正極集電体露出部の厚みを測定した。それぞれ任意の５点で測定して平均値を求めた。正極シートの厚みから正極集電体露出部の厚みを差し引いて正極活物質層の厚みを算出した。
正極シートを、直径１６ｍｍの円形に打ち抜いた測定試料を５枚準備した。
各測定試料の質量を精密天秤にて秤量し、測定結果から、予め測定した正極集電体の質量を差し引くことにより、測定試料中の正極活物質層の質量を算出した。各測定値の平均値から前記式（１）に基づいて、正極活物質層の体積密度を算出した。 [Method for measuring volume density]
Using a microgauge, the thickness of the positive electrode sheet and the thickness of the exposed portion of the positive electrode current collector were measured. Each was measured at arbitrary five points and an average value was obtained. The thickness of the positive electrode active material layer was calculated by subtracting the thickness of the positive electrode current collector exposed portion from the thickness of the positive electrode sheet.
Five measurement samples were prepared by punching a positive electrode sheet into a circle with a diameter of 16 mm.
The mass of each measurement sample was weighed with a precision balance, and the mass of the positive electrode active material layer in the measurement sample was calculated by subtracting the previously measured mass of the positive electrode current collector from the measurement result. The volume density of the positive electrode active material layer was calculated based on the above formula (1) from the average value of each measured value.

＜評価方法＞
［耐熱性の評価：出力維持率の測定］
（１）非水電解質二次電池（初期状態）について、下記の方法で初期出力可能な電力（単位：Ｗｈ）を測定した。
定格容量が１．５Ａｈとなるように非水電解質二次電池（セル）を作製した。得られたセルに対し、２５℃環境下で、０．２Ｃレート（すなわち、３００ｍＡ）で一定電流にて終止電圧３．６Ｖで充電を行った後、一定電圧にて前記充電電流の１／１０を終止電流（すなわち、３０ｍＡ）として充電を行った。
次いで、２５℃環境下で、放電を１．０Ｃレート（すなわち、１５００ｍＡ）で一定電流にて終止電圧３．０Ｖで行った。このときの放電電力を初期状態で出力可能な電力（以下、「初期出力」ともいう）Ｅ１とした。
（２）次いで、２５℃環境下で、セルの０．２Ｃレート（すなわち、３００ｍＡ）で一定電流にて終止電圧３．６Ｖで充電を行った後、一定電圧にて前記充電電流の１／１０を終止電流（すなわち、３０ｍＡ）として満充電状態への調整を行った。
（３）前記（１）の測定、および前記（２）の満充電への調整を終えた非水電解質二次電池を、８０℃の雰囲気中に２０日間貯蔵した。
（４）前記（３）の貯蔵を終えた後、下記の方法で貯蔵後出力可能な電力（単位：Ｗｈ）を測定した。
まず、２５℃環境下で、放電を０．２Ｃレート（すなわち、３００ｍＡ）で一定電流にて終止電圧２．５Ｖで行った。
次いで、２５℃環境下で、充電を０．２Ｃレート（すなわち、３００ｍＡ）で一定電流にて終止電圧３．６Ｖで充電を行った後、一定電圧にて前記充電電流の１／１０を終止電流（すなわち、３０ｍＡ）として充電を行った。
次いで、２５℃環境下で、放電を１．０Ｃレート（すなわち、１５００ｍＡ）で一定電流にて終止電圧３．０Ｖで行った。このときの放電電力を貯蔵後の状態で出力可能な電力（以下、「貯蔵後出力」ともいう）Ｅ２とした。
（５）前記（１）で得た初期出力Ｅ１に対する、前記（４）で得た貯蔵後出力Ｅ２の割合を下記式により求め、出力維持率（単位：％）とした。
出力維持率＝（Ｅ２／Ｅ１）×１００ <Evaluation method>
[Evaluation of heat resistance: measurement of output retention rate]
(1) Regarding the non-aqueous electrolyte secondary battery (initial state), the initial output power (unit: Wh) was measured by the following method.
A non-aqueous electrolyte secondary battery (cell) was produced so as to have a rated capacity of 1.5 Ah. The resulting cell was charged at a constant current of 0.2 C rate (i.e., 300 mA) at a constant current at a final voltage of 3.6 V under an environment of 25 ° C., and then charged at a constant voltage of 1/10 of the charging current. was set as the final current (that is, 30 mA).
Then, in a 25° C. environment, discharge was performed at a constant current of 1.0 C rate (ie, 1500 mA) with a final voltage of 3.0 V. The discharge power at this time was defined as the power that can be output in the initial state (hereinafter also referred to as "initial output") E1.
(2) Then, in an environment of 25° C., the cell is charged at a constant current at a rate of 0.2 C (that is, 300 mA) at a final voltage of 3.6 V, and then at a constant voltage of 1/10 of the charging current. was set as the final current (ie, 30 mA) and adjusted to the fully charged state.
(3) The non-aqueous electrolyte secondary battery subjected to the measurement in (1) and the adjustment to full charge in (2) was stored in an atmosphere of 80° C. for 20 days.
(4) After completing the storage in (3) above, the power (unit: Wh) that can be output after storage was measured by the following method.
First, in a 25° C. environment, discharge was performed at a constant current of 0.2 C rate (that is, 300 mA) and a final voltage of 2.5 V.
Then, in an environment of 25 ° C., after charging at a constant current of 0.2 C rate (that is, 300 mA) and a final voltage of 3.6 V, 1/10 of the charging current at a constant voltage is charged to the final current. (that is, 30 mA).
Then, in a 25° C. environment, discharge was performed at a constant current of 1.0 C rate (ie, 1500 mA) with a final voltage of 3.0 V. The discharge power at this time was defined as the power that can be output in the state after storage (hereinafter also referred to as "post-storage output") E2.
(5) The ratio of the post-storage output E2 obtained in (4) above to the initial output E1 obtained in (1) above was determined by the following formula and defined as an output retention rate (unit: %).
Output maintenance rate = (E2/E1) x 100

＜製造例１：負極の製造＞
負極活物質である人造黒鉛１００質量部と、結着材であるスチレンブタジエンゴム１．５質量部と、増粘材であるカルボキシメチルセルロースＮａ１．５質量部と、溶媒である水とを混合し、固形分５０質量％の負極製造用組成物を得た。
得られた負極製造用組成物を、銅箔（厚さ８μｍ）の両面上にそれぞれ塗工し、１００℃で真空乾燥した後、２ｋＮの荷重で加圧プレスして負極シートを得た。上記の方法で負極活物質層の単位面積あたりの質量を測定した。その結果を表５に示す。
得られた負極シートを打ち抜き、負極とした。 <Production Example 1: Production of Negative Electrode>
100 parts by mass of artificial graphite as a negative electrode active material, 1.5 parts by mass of styrene-butadiene rubber as a binder, 1.5 parts by mass of carboxymethyl cellulose Na as a thickener, and water as a solvent are mixed, A composition for manufacturing a negative electrode having a solid content of 50% by mass was obtained.
The obtained composition for manufacturing a negative electrode was coated on both sides of a copper foil (thickness: 8 μm), dried in vacuum at 100° C., and then pressed under a load of 2 kN to obtain a negative electrode sheet. The mass per unit area of the negative electrode active material layer was measured by the method described above. Table 5 shows the results.
The obtained negative electrode sheet was punched out to obtain a negative electrode.

＜製造例２：集電体被覆層を有する集電体の製造＞
カーボンブラック１００質量部と、結着材であるポリフッ化ビニリデン４０質量部と、溶媒であるＮ－メチルピロリドン（ＮＭＰ）とを混合してスラリーを得た。ＮＭＰの使用量はスラリーを塗工するのに必要な量とした。
得られたスラリーを厚さ１５μｍのアルミニウム箔（正極集電体本体）の表裏両面に、乾燥後の集電体被覆層の厚さ（両面合計）が２μｍとなるように、グラビア法で塗工し、乾燥し溶媒を除去して正極集電体とした。両面それぞれの集電体被覆層は、塗工量及び厚みが互いに均等になるように形成した。 <Production Example 2: Production of current collector having current collector coating layer>
A slurry was obtained by mixing 100 parts by mass of carbon black, 40 parts by mass of polyvinylidene fluoride as a binder, and N-methylpyrrolidone (NMP) as a solvent. The amount of NMP used was the amount necessary for coating the slurry.
The resulting slurry is applied to both the front and back surfaces of a 15 μm thick aluminum foil (positive electrode current collector body) by a gravure method so that the thickness of the current collector coating layer after drying (both sides total) is 2 μm. and dried to remove the solvent to obtain a positive electrode current collector. The current collector coating layers on both sides were formed so that the coating amount and thickness were uniform.

＜例Ａ１～Ａ５＞
例Ａ１～Ａ３は実施例、例Ａ４、Ａ５は比較例である。
正極活物質粒子として、下記の２種の活物質被覆部を有するリン酸鉄リチウム粒子（以下「カーボンコート活物質」ともいう。）を用いた。
カーボンコート活物質（１）：平均粒子径１μｍ、炭素含有量１．５質量％。
カーボンコート活物質（２）：平均粒子径１０μｍ、炭素含有量２．５質量％。
カーボンコート活物質（１）、（２）のいずれも、活物質被覆部の厚さは１～１００ｎｍの範囲内であった。
導電助剤としてカーボンブラック（ＣＢ）又はカーボンナノチューブ（ＣＮＴ）を用いた。ＣＢ及びＣＮＴは不純物が定量限界以下であり、炭素含有量１００質量％とみなすことができる。
結着材としてポリフッ化ビニリデン（ＰＶＤＦ）を用いた。
溶媒としてＮ－メチルピロリドン（ＮＭＰ）を用いた。
正極集電体として、製造例２で得た集電体被覆層を有するアルミニウム箔を用いた。 <Examples A1 to A5>
Examples A1 to A3 are working examples, and examples A4 and A5 are comparative examples.
As the positive electrode active material particles, lithium iron phosphate particles (hereinafter also referred to as “carbon-coated active material”) having the following two kinds of active material coating portions were used.
Carbon-coated active material (1): average particle diameter of 1 μm, carbon content of 1.5% by mass.
Carbon-coated active material (2): average particle size of 10 μm, carbon content of 2.5% by mass.
Both of the carbon-coated active materials (1) and (2) had a thickness of the active material coating within a range of 1 to 100 nm.
Carbon black (CB) or carbon nanotube (CNT) was used as a conductive aid. CB and CNT have impurities below the limit of quantification, and can be regarded as having a carbon content of 100% by mass.
Polyvinylidene fluoride (PVDF) was used as a binder.
N-methylpyrrolidone (NMP) was used as solvent.
As the positive electrode current collector, the aluminum foil having the current collector coating layer obtained in Production Example 2 was used.

以下の方法で正極活物質層を形成した。
表１に示す配合の正極活物質粒子、導電助剤、結着材及び溶媒（ＮＭＰ）をミキサーにて混合して正極製造用組成物を得た。溶媒の使用量は、正極製造用組成物を塗工するのに必要な量とした。なお、表中における正極活物質粒子、導電助剤及び結着材の配合量は、溶媒以外の合計（即ち、正極活物質粒子、導電助剤及び結着材の合計量）を１００質量％とするときの割合である。
得られた正極製造用組成物を、正極集電体の両面上にそれぞれ塗工し、予備乾燥後、１２０℃環境で真空乾燥して正極活物質層を形成した。得られた積層物を加圧プレスして正極シートを得た。塗工量（両面合計）、正極活物質層の厚み（両面合計）、及び体積密度を表１に示す。両面それぞれの正極活物質層は、塗工量及び厚みが互いに均等になるように形成した。
得られた正極シートを打ち抜き、正極とした。 A positive electrode active material layer was formed by the following method.
The positive electrode active material particles, the conductive aid, the binder and the solvent (NMP) having the compositions shown in Table 1 were mixed in a mixer to obtain a composition for manufacturing a positive electrode. The amount of the solvent used was the amount necessary for coating the composition for manufacturing a positive electrode. In addition, the compounding amounts of the positive electrode active material particles, the conductive aid, and the binder in the table are based on the total amount other than the solvent (that is, the total amount of the positive electrode active material particles, the conductive aid, and the binder) being 100% by mass. It is the ratio when
The obtained composition for manufacturing a positive electrode was applied on both sides of a positive electrode current collector, and after preliminary drying, vacuum drying was performed in an environment of 120° C. to form a positive electrode active material layer. The resulting laminate was pressure-pressed to obtain a positive electrode sheet. Table 1 shows the coating amount (both sides total), the thickness of the positive electrode active material layer (both sides total), and the volume density. The positive electrode active material layers on both sides were formed so that the coating amount and thickness were uniform.
The obtained positive electrode sheet was punched out to obtain a positive electrode.

得られた正極シートについて、上記の方法で正極活物質層の断面の拡がり抵抗値分布を測定し、表２に示す各項目の値を求めた。また正極活物質層の総質量に対する導電性炭素含有量を求めた。結果を表２に示す。
図３は、例Ａ１の拡がり抵抗値分布の測定結果を示したマッピング画像であり、図４は、例Ａ４のマッピング画像である。図５は例Ａ１、Ａ３の拡がり抵抗値分布を表すグラフであり、横軸は拡がり抵抗値（単位：ｌｏｇΩ）を表し、縦軸は抵抗値４．０～１２．５（ｌｏｇΩ）の頻度合計を１００％としたときの相対頻度（単位：％）を表す。
カーボンコート活物質の炭素含有量と配合量、及び導電助剤の炭素含有量と配合量に基づいて、正極活物質層の総質量に対する導電性炭素の含有量を算出した。上記≪導電性炭素含有量の測定方法≫に記載の方法を用いて確認することも可能である。 For the obtained positive electrode sheet, the spreading resistance value distribution of the cross section of the positive electrode active material layer was measured by the method described above, and the values of each item shown in Table 2 were obtained. Also, the conductive carbon content relative to the total mass of the positive electrode active material layer was determined. Table 2 shows the results.
FIG. 3 is a mapping image showing the measurement results of the spreading resistance value distribution of Example A1, and FIG. 4 is a mapping image of Example A4. FIG. 5 is a graph showing the spreading resistance value distribution of Examples A1 and A3, the horizontal axis represents the spreading resistance value (unit: log Ω), and the vertical axis represents the total frequency of resistance values 4.0 to 12.5 (log Ω). represents the relative frequency (unit: %) when is 100%.
Based on the carbon content and compounding amount of the carbon-coated active material and the carbon content and compounding amount of the conductive aid, the content of conductive carbon with respect to the total mass of the positive electrode active material layer was calculated. It is also possible to confirm using the method described in the above <<Method for measuring conductive carbon content>>.

以下の方法で、図２に示す構成の非水電解質二次電池を製造した。
エチレンカーボネート（ＥＣ）とジエチルカーボネート（ＤＥＣ）を、ＥＣ：ＤＥＣの体積比が３：７となるように混合した溶媒に、電解質としてＬｉＰＦ６を１モル／リットルとなるように溶解して、非水電解液を調製した。
本例で得た正極と、製造例１で得た負極とを、セパレータを介して交互に積層し、最外層が負極である電極積層体を作製した。セパレータとしては、ポリオレフィンフィルム（厚さ１５μｍ）を用いた。
電極積層体を作製する工程では、まず、セパレータ２と正極１とを積層し、その後、セパレータ２上に負極３を積層した。
電極積層体の正極集電体露出部１３及び負極集電体露出部３３のそれぞれに、端子用タブを電気的に接続し、端子用タブが外部に突出するように、アルミラミネートフィルムで電極積層体を挟み、三辺をラミネート加工して封止した。
続いて、封止せずに残した一辺から非水電解液を注入し、真空封止して非水電解質二次電池（ラミネートセル）を製造した。
上記の方法で、高温貯蔵前後の出力維持率を測定し耐熱性を評価した。結果を表２に示す。 A non-aqueous electrolyte secondary battery having the configuration shown in FIG. 2 was manufactured by the following method.
Ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed so that the volume ratio of EC:DEC was 3:7. An aqueous electrolyte was prepared.
The positive electrode obtained in this example and the negative electrode obtained in Production Example 1 were alternately laminated via a separator to prepare an electrode laminate having the negative electrode as the outermost layer. A polyolefin film (thickness: 15 μm) was used as the separator.
In the process of producing the electrode laminate, first, the separator 2 and the positive electrode 1 were laminated, and then the negative electrode 3 was laminated on the separator 2 .
A terminal tab is electrically connected to each of the positive electrode current collector exposed portion 13 and the negative electrode current collector exposed portion 33 of the electrode laminate, and the electrodes are stacked with an aluminum laminate film so that the terminal tab protrudes to the outside. The body was sandwiched, and three sides were laminated and sealed.
Subsequently, a non-aqueous electrolyte was injected from one side that was left unsealed, and vacuum-sealed to manufacture a non-aqueous electrolyte secondary battery (laminate cell).
The heat resistance was evaluated by measuring the output retention rate before and after high-temperature storage by the above method. Table 2 shows the results.

Figure 2023024425000002
Figure 2023024425000002

Figure 2023024425000003
Figure 2023024425000003

表２の結果に示されるように、正極活物質層の断面において抵抗値が４．０～６．０（ｌｏｇΩ）である部分が５．０％以下と少ない例Ａ１～Ａ３は、高温環境に貯蔵されても出力維持率が高く、耐熱性が良好であった。高温下で劣化反応しやすい低抵抗な部分が正極活物質層中にほとんど存在しないため、抵抗の増大が生じ難かったと考えられる。
例Ａ１と例Ａ３を比べると、導電助剤を含まない例Ａ１の方が、抵抗値４．０～６．０（ｌｏｇΩ）の頻度合計が少なく、出力維持率がより高かった。
例Ａ２は、例Ａ１において導電助剤の添加量を増やさずに、導電性炭素の含有量を増大させた例である。例Ａ１に比べて抵抗値４．０～６．０（ｌｏｇΩ）の頻度合計がより少なく、抵抗値６．０～９．０（ｌｏｇΩ）の平均頻度Ｂがより多くなり、出力維持率がさらに向上した。 As shown in the results of Table 2, in Examples A1 to A3, the portion having a resistance value of 4.0 to 6.0 (log Ω) in the cross section of the positive electrode active material layer is as small as 5.0% or less. Even when stored, the output retention rate was high and the heat resistance was good. It is conceivable that the increase in resistance was difficult to occur because there was almost no low-resistance portion in the positive electrode active material layer, which is likely to undergo a deterioration reaction at high temperatures.
Comparing Example A1 and Example A3, Example A1, which does not contain a conductive aid, has a lower total frequency of resistance values of 4.0 to 6.0 (log Ω) and a higher output retention rate.
Example A2 is an example in which the content of conductive carbon is increased without increasing the amount of the conductive additive added in Example A1. Compared to Example A1, the total frequency of resistance values 4.0 to 6.0 (log Ω) is less, the average frequency B of resistance values 6.0 to 9.0 (log Ω) is greater, and the output maintenance rate is further increased. Improved.

一方、抵抗値４．０～６．０（ｌｏｇΩ）の頻度合計が５．０％を超える例Ａ４、Ａ５は、例Ａ１～Ａ３と比べて高温環境に貯蔵されたときの出力維持率が顕著に低く、耐熱性が劣った。図４のマッピング画像からわかるように、例Ａ４の正極活物質層中には低抵抗な部分が局所的に点在している。このような低抵抗な部分が高温環境下において活性点となって劣化反応が生じたと考えられる。 On the other hand, Examples A4 and A5, in which the total frequency of resistance values 4.0 to 6.0 (log Ω) exceeds 5.0%, have a remarkable output retention rate when stored in a high temperature environment compared to Examples A1 to A3. was low, and the heat resistance was poor. As can be seen from the mapping image of FIG. 4, the positive electrode active material layer of Example A4 is locally dotted with low resistance portions. It is considered that such a low-resistance portion became an active point in a high-temperature environment, and a deterioration reaction occurred.

＜評価方法＞
［容量維持率の測定方法（急速充放電サイクル試験）］
定格容量１Ａｈの非水電解質二次電池とし、３．５Ｃレート、３．８Ｖで充電し１０秒間休止し、次いで、３．５Ｃレート、２．０Ｖで放電し１０秒間休止する充放電サイクルを１０００回繰り返し、その後０．２Ｃレート、２．５Ｖで放電した際の放電容量Ｂを測定した。充放電サイクルに供する前の非水電解質二次電池の放電容量Ａで放電容量Ｂを除してサイクル容量維持率（％）とした。
前記サイクル容量維持率の値が高いほど、急速充放電サイクル試験後の劣化が生じ難く、耐久性に優れる。
前記サイクル容量維持率は、例えば５０％以上が好ましく、５５％以上がより好ましく、６０％以上がさらに好ましい。 <Evaluation method>
[Method for measuring capacity retention rate (rapid charge-discharge cycle test)]
A non-aqueous electrolyte secondary battery with a rated capacity of 1 Ah was charged at a rate of 3.5 C and 3.8 V and rested for 10 seconds, then discharged at a rate of 3.5 C and 2.0 V and rested for 10 seconds. After that, the battery was discharged at a rate of 0.2C and 2.5V, and the discharge capacity B was measured. The cycle capacity retention rate (%) was obtained by dividing the discharge capacity B by the discharge capacity A of the non-aqueous electrolyte secondary battery before being subjected to charge-discharge cycles.
The higher the value of the cycle capacity retention rate, the less likely deterioration occurs after the rapid charge/discharge cycle test, and the better the durability.
For example, the cycle capacity retention rate is preferably 50% or more, more preferably 55% or more, and even more preferably 60% or more.

＜例Ｂ１～Ｂ６＞
例Ｂ１～Ｂ４は実施例、例Ｂ５、Ｂ６は比較例である。
正極活物質粒子として、活物質被覆部を有するリン酸鉄リチウム粒子（以下「カーボンコート活物質」ともいう。）を用いた。活物質被覆部は導電性炭素材料であり、炭素含有量１００質量％とみなすことができる。カーボンコート活物質は下記の３種を用意した。
カーボンコート活物質（１）：粒子本体９８．９質量％、活物質被覆部１．１質量％。
カーボンコート活物質（２）：粒子本体９７．８質量％、活物質被覆部２．２質量％。
カーボンコート活物質（３）：粒子本体９８．９質量％、活物質被覆部１．１質量％。
カーボンコート活物質（１）～（３）のいずれも、活物質被覆部の厚さは１～１００ｎｍの範囲内であった。カーボンコート活物質（１）～（３）は活物質被覆部の抵抗率が互いに異なる。 <Examples B1 to B6>
Examples B1 to B4 are working examples, and examples B5 and B6 are comparative examples.
As the positive electrode active material particles, lithium iron phosphate particles having an active material coating portion (hereinafter also referred to as “carbon-coated active material”) were used. The active material coating portion is a conductive carbon material, and can be considered to have a carbon content of 100% by mass. The following three types of carbon-coated active materials were prepared.
Carbon-coated active material (1): Particle main body 98.9% by mass, active material coating portion 1.1% by mass.
Carbon-coated active material (2): Particle main body 97.8% by mass, active material coating portion 2.2% by mass.
Carbon-coated active material (3): Particle main body 98.9% by mass, active material coating portion 1.1% by mass.
In all of the carbon-coated active materials (1) to (3), the thickness of the active material coating portion was within the range of 1 to 100 nm. The carbon-coated active materials (1) to (3) differ from each other in the resistivity of the active material coating portion.

導電助剤として下記の２種を用意した。
アセチレンブラック（ＡＢ）：真密度ρ６２．０ｇ／ｃｍ３、抵抗率Ｒ４０．０１６Ω・ｃｍ。
カーボンナノチューブ（ＣＮＴ）：真密度ρ６２．２ｇ／ｃｍ３、抵抗率Ｒ４０．００５Ω・ｃｍ。
前記ＡＢ及びＣＮＴは不純物が定量限界以下であり、炭素含有量１００質量％とみなすことができる。
各導電助剤の抵抗率Ｒ４は上記≪導電助剤の抵抗率Ｒ４の測定方法≫で測定した。導電助剤の粉体抵抗率Ｒ３を測定する際の加圧力は１２ＭＰａとした。 The following two types were prepared as conductive aids.
Acetylene black (AB): True density ρ 6 2.0 g/cm 3 , resistivity R 4 0.016 Ω·cm.
Carbon nanotube (CNT): true density ρ 6 2.2 g/cm 3 , resistivity R 4 0.005 Ω·cm.
AB and CNT have impurities below the limit of quantification, and can be regarded as having a carbon content of 100% by mass.
The resistivity R4 of each conductive aid was measured by the above <<Method for measuring resistivity R4 of conductive aid>>. The applied pressure was 12 MPa when measuring the powder resistivity R3 of the conductive aid.

結着材としてポリフッ化ビニリデン（ＰＶＤＦ）を用いた。
溶媒としてＮ－メチルピロリドン（ＮＭＰ）を用いた。
正極集電体として、製造例２で得た集電体被覆層を有するアルミニウム箔を用いた。 Polyvinylidene fluoride (PVDF) was used as a binder.
N-methylpyrrolidone (NMP) was used as solvent.
As the positive electrode current collector, the aluminum foil having the current collector coating layer obtained in Production Example 2 was used.

［正極の製造］
以下の方法で正極活物質層を形成した。
表３に示す正極活物質粒子、導電助剤、結着材及び溶媒（ＮＭＰ）をミキサーにて混合して正極製造用組成物を得た。溶媒の使用量は、正極製造用組成物を塗工するのに必要な量とした。なお、表中における結着材の配合量は、溶媒以外の合計（即ち、正極活物質粒子、導電助剤及び結着材の合計量）を１００質量％とするときの割合である。
得られた正極製造用組成物を、正極集電体の両面上にそれぞれ塗工し、予備乾燥後、１２０℃環境で真空乾燥して正極活物質層を形成した。得られた積層物を加圧プレスして正極シートを得た。両面それぞれの正極活物質層は、塗工量及び厚みが互いに均等になるように形成した。塗工量（両面合計）は３３ｍｇ／ｃｍ２、正極活物質層の厚み（両面合計）は１４３μｍであった。
得られた正極シートを打ち抜き、正極とした。 [Manufacturing of positive electrode]
A positive electrode active material layer was formed by the following method.
The positive electrode active material particles, conductive aid, binder and solvent (NMP) shown in Table 3 were mixed in a mixer to obtain a composition for manufacturing a positive electrode. The amount of the solvent used was the amount necessary for coating the composition for manufacturing a positive electrode. The amount of the binder compounded in the table is the ratio when the total amount other than the solvent (that is, the total amount of the positive electrode active material particles, the conductive aid, and the binder) is 100% by mass.
The obtained composition for manufacturing a positive electrode was applied on both sides of a positive electrode current collector, and after preliminary drying, vacuum drying was performed in an environment of 120° C. to form a positive electrode active material layer. The resulting laminate was pressure-pressed to obtain a positive electrode sheet. The positive electrode active material layers on both sides were formed so that the coating amount and thickness were uniform. The coating amount (both sides total) was 33 mg/cm 2 , and the positive electrode active material layer thickness (both sides total) was 143 μm.
The obtained positive electrode sheet was punched out to obtain a positive electrode.

得られた正極シートについて、上記≪活物質被覆部の抵抗率Ｒ２の測定方法≫で活物質被覆部の抵抗率Ｒ２を測定した。
（ｉ）正極集電体上の正極活物質層を削り採った粉体を測定対象粉体とし、上記＜粉体抵抗率Ｒ１の測定方法＞で粉体抵抗率Ｒ１を及び質量密度ρ１を測定した。
測定装置は日東精工アナリテック社製、粉体抵抗測定システム（型式番号：ＭＣＰ－ＰＤ５１）を用いたた。真空乾燥後のサンプル２ｇを半径１０ｍｍの測定セルに投入し、５０ＭＰａにて加圧した際の粉体抵抗率（単位：Ω・ｃｍ）及びサンプル厚みを測定した。測定条件は、電極間隔３ｍｍ、電極半径０．７ｍｍ、４探針プローブとした。サンプル数は３とし、平均値を求めた。得られた粉体抵抗率Ｒ１を表３に示す。
（ｉｉ）正極活物質層の総質量に対する活物質被覆部の含有量ｍ１を、カーボンコート活物質の活物質被覆部の含有量と配合量に基づいて算出した。得られたｍ１を表３に示す。
ｍ１は上記≪導電性炭素含有量の測定方法≫を用いて確認することも可能である。
（ｉｉｉ）上記＜体積比率Ｑ１の求め方＞で体積比率Ｑ１を求めた。ρ３＝３．６、ρ４＝２．０の理論値を用いた。
（ｉＶ）上記式（１）により活物質被覆部の抵抗率Ｒ２を求めた。結果を表３に示す。 For the obtained positive electrode sheet, the resistivity R2 of the active material coating portion was measured according to the above <<Method for measuring resistivity R2 of the active material coating portion>>.
(i) The powder obtained by scraping off the positive electrode active material layer on the positive electrode current collector is used as the powder to be measured, and the powder resistivity R 1 and the mass density ρ are measured by the above <Method for measuring powder resistivity R 1 >. 1 was measured.
As a measuring device, a powder resistance measuring system (model number: MCP-PD51) manufactured by Nitto Seiko Analytic Tech was used. 2 g of the vacuum-dried sample was put into a measurement cell with a radius of 10 mm, and the powder resistivity (unit: Ω·cm) and the sample thickness were measured under pressure of 50 MPa. The measurement conditions were an electrode interval of 3 mm, an electrode radius of 0.7 mm, and a 4-point probe. The number of samples was set to 3, and the average value was obtained. Table 3 shows the powder resistivity R1 obtained.
(ii) The content m1 of the active material covering portion with respect to the total mass of the positive electrode active material layer was calculated based on the content of the active material covering portion of the carbon coat active material and the blending amount. Table 3 shows the m 1 obtained.
m1 can also be confirmed using the above <<Method for measuring conductive carbon content>>.
(iii) The volume ratio Q1 was determined by the above <How to determine the volume ratio Q1 >. Theoretical values of ρ 3 =3.6 and ρ 4 =2.0 were used.
(iv) The resistivity R2 of the active material-coated portion was obtained from the above formula (1). Table 3 shows the results.

得られた正極シートについて、上記≪導電助剤の含有量の測定方法≫で正極活物質層の総質量に対する導電助剤の含有量α２を測定した。正極活物質層に対する導電助剤の体積割合α１を求める際の＜拡がり抵抗値分布の測定方法＞は下記の条件で実施した。結果を表３に示す。
（拡がり抵抗値分布の測定条件）
正極活物質層の厚さ方向に平行な断面を測定対象とし、ＳＳＲＭを用い、下記の条件で拡がり抵抗値分布を測定した。
（使用装置）Ｂｒｕｋｅｒ社製、製品名：ＮａｎｏＳｃｏｐｅＶ ＤｉｍｅｎｓｉｏｎＩｃｏｎ、Ｇｌｏｖｅｂｏｘ。
（試料の調製）正極シートから切り出した試験片をエポキシ樹脂で包埋した後、ブロードイオンビーム加工により切断して断面を作製し、不活性雰囲気下で測定装置内に導入した。
（測定条件）
走査モード：コンタクトモードと拡がり抵抗の同時測定。
探針（Ｔｉｐ）：ダイヤモンドコートシリコンカンチレバー（ＤＤＥＳＰ １０）。
測定環境：室温、高純度Ａｒガス雰囲気中（Ｈ２Ｏ＝０．１ｐｐｍ、Ｏ２＝０．１ｐｐｍ）。
印加電圧：ＤＣバイアス電圧＝＋２．０Ｖ。
スキャンサイズ：６０μｍ×６０μｍ。
測定点の数（データ点数）：１０２４×１０２４。 With respect to the obtained positive electrode sheet, the content α2 of the conductive support agent relative to the total mass of the positive electrode active material layer was measured according to the <<method for measuring the content of the conductive support agent>> described above. <Method for measuring spreading resistance value distribution> for determining the volume ratio α1 of the conductive aid to the positive electrode active material layer was performed under the following conditions. Table 3 shows the results.
(Measurement conditions for spreading resistance value distribution)
Using a cross section parallel to the thickness direction of the positive electrode active material layer as a measurement target, the spreading resistance value distribution was measured using SSRM under the following conditions.
(Apparatus used) Bruker, product name: NanoScopeV Dimension Icon, Glovebox.
(Preparation of Sample) A test piece cut out from the positive electrode sheet was embedded in an epoxy resin, cut by broad ion beam processing to prepare a cross section, and introduced into a measuring apparatus under an inert atmosphere.
(Measurement condition)
Scan mode: Simultaneous measurement of contact mode and spreading resistance.
Tip: Diamond coated silicon cantilever (DDESP 10).
Measurement environment: room temperature, high-purity Ar gas atmosphere (H 2 O=0.1 ppm, O 2 =0.1 ppm).
Applied voltage: DC bias voltage = +2.0V.
Scan size: 60 μm×60 μm.
Number of measurement points (number of data points): 1024×1024.

例Ｂ１～Ｂ６において、活物質被覆部の抵抗率Ｒ２はいずれも０．１０Ω・ｃｍより高く、導電助剤の抵抗率Ｒ４はいずれも０．１０Ω・ｃｍ以下であった。例Ｂ１～３の正極活物質層は導電助剤を含まないため、低抵抗導電性炭素材料（Ｃ１）の含有量はゼロである。例Ｂ４～Ｂ６の正極活物質層における低抵抗導電性炭素材料（Ｃ１）の含有量は、導電助剤の含有量と同じになる。
正極活物質層の総質量に対する、低抵抗導電性炭素材料（Ｃ１）の含有量を表３に示す。 In Examples B1 to B6, the resistivity R 2 of the active material coating portion was all higher than 0.10 Ω·cm, and the resistivity R 4 of the conductive aid was all 0.10 Ω·cm or less. Since the positive electrode active material layers of Examples B1 to B3 do not contain a conductive aid, the content of the low-resistance conductive carbon material (C1) is zero. The content of the low-resistance conductive carbon material (C1) in the positive electrode active material layers of Examples B4 to B6 is the same as the content of the conductive aid.
Table 3 shows the content of the low-resistance conductive carbon material (C1) with respect to the total mass of the positive electrode active material layer.

［非水電解質二次電池の製造・評価］
各例で得た正極を用い、以下の方法で、図２に示す構成の非水電解質二次電池を製造した。
エチレンカーボネート（ＥＣ）とジエチルカーボネート（ＤＥＣ）を、ＥＣ：ＤＥＣの体積比が３：７となるように混合した溶媒に、電解質としてＬｉＰＦ６を１モル／リットルとなるように溶解して、非水電解液を調製した。
各例で得た正極と、製造例１で得た負極とを、セパレータを介して交互に積層し、最外層が負極である電極積層体を作製した。セパレータとしては、ポリオレフィンフィルム（厚さ１５μｍ）を用いた。
電極積層体を作製する工程では、まず、セパレータ２と正極１とを積層し、その後、セパレータ２上に負極３を積層した。
電極積層体の正極集電体露出部１３及び負極集電体露出部３３のそれぞれに、端子用タブを電気的に接続し、端子用タブが外部に突出するように、アルミラミネートフィルムで電極積層体を挟み、三辺をラミネート加工して封止した。
続いて、封止せずに残した一辺から非水電解液を注入し、真空封止して非水電解質二次電池（ラミネートセル）を製造した。
上記の方法で、サイクル容量維持率を測定し耐久性を評価した。結果を表３に示す。 [Manufacturing and evaluation of non-aqueous electrolyte secondary battery]
Using the positive electrode obtained in each example, a non-aqueous electrolyte secondary battery having the configuration shown in FIG. 2 was manufactured by the following method.
Ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed so that the volume ratio of EC:DEC was 3:7. An aqueous electrolyte was prepared.
The positive electrode obtained in each example and the negative electrode obtained in Production Example 1 were alternately laminated via a separator to prepare an electrode laminate having the negative electrode as the outermost layer. A polyolefin film (thickness: 15 μm) was used as the separator.
In the process of producing the electrode laminate, first, the separator 2 and the positive electrode 1 were laminated, and then the negative electrode 3 was laminated on the separator 2 .
A terminal tab is electrically connected to each of the positive electrode current collector exposed portion 13 and the negative electrode current collector exposed portion 33 of the electrode laminate, and the electrodes are stacked with an aluminum laminate film so that the terminal tab protrudes to the outside. The body was sandwiched, and three sides were laminated and sealed.
Subsequently, a non-aqueous electrolyte was injected from one side that was left unsealed, and vacuum-sealed to manufacture a non-aqueous electrolyte secondary battery (laminate cell).
By the above method, the cycle capacity retention rate was measured and the durability was evaluated. Table 3 shows the results.

Figure 2023024425000004
Figure 2023024425000004

表３の結果に示されるように、正極活物質層の総質量に対して、抵抗率が０．１０Ω・ｃｍ以下の低抵抗導電性炭素材料（Ｃ１）の含有量が０．５質量％以下である例Ｂ１～Ｂ４は、急速充放電サイクル試験における容量維持率が高く、耐久性に優れていた。
なお、例Ｂ１～Ｂ４は、抵抗率が０．０２Ω・ｃｍ以下である低抵抗導電性炭素材料（Ｃ２）の含有量も０．５質量％以下であった。
一方、正極活物質層の総質量に対して、低抵抗導電性炭素材料（Ｃ１）が０．５質量％を超える例Ｂ５、Ｂ６は、急速充放電サイクル試験における容量維持率が低く、耐久性が劣った。
例Ｂ５、Ｂ６は、急速充放電サイクル時に、抵抗率が低い導電性炭素材料に電流が集中することによって正極と電解液との副反応の起点となり、電解液の分解が進行しやすいためと考えられる。電解液の分解およびその分解生成物と電極の反応により抵抗成分が上昇すると、急速充放電による電池の劣化が進行しやすい。
例Ｂ１～Ｂ４は、抵抗率が低い導電性炭素材料の含有量を低く抑えたことにより、電解液の分解の進行が抑制され、サイクル特性が改善したと考えられる。
特に、正極活物質粒子の総質量に対する活物質被覆部の含有量が多い例Ｂ２は、例Ｂ１～Ｂ４のなかでも正極活物質層の粉体抵抗率が低く、急速充放電サイクル容量維持率がより向上した。 As shown in the results of Table 3, the content of the low-resistance conductive carbon material (C1) having a resistivity of 0.10 Ω·cm or less is 0.5% by mass or less with respect to the total mass of the positive electrode active material layer. Examples B1 to B4, which are , had a high capacity retention rate in the rapid charge-discharge cycle test and were excellent in durability.
In Examples B1 to B4, the content of the low-resistance conductive carbon material (C2) having a resistivity of 0.02 Ω·cm or less was also 0.5% by mass or less.
On the other hand, Examples B5 and B6, in which the low-resistance conductive carbon material (C1) exceeds 0.5% by mass with respect to the total mass of the positive electrode active material layer, have a low capacity retention rate in the rapid charge-discharge cycle test, and durability was inferior.
In Examples B5 and B6, it is believed that during the rapid charge/discharge cycle, the concentration of current in the conductive carbon material with low resistivity causes a side reaction between the positive electrode and the electrolytic solution, and the electrolytic solution is likely to decompose. be done. When the resistance component increases due to the decomposition of the electrolytic solution and the reaction between the decomposition product and the electrode, deterioration of the battery due to rapid charge/discharge tends to progress.
It is believed that in Examples B1 to B4, the content of the conductive carbon material with low resistivity was kept low, thereby suppressing the progress of decomposition of the electrolytic solution and improving the cycle characteristics.
In particular, Example B2, in which the content of the active material coating portion with respect to the total mass of the positive electrode active material particles is large, has a low powder resistivity of the positive electrode active material layer among Examples B1 to B4, and a rapid charge-discharge cycle capacity retention rate. improved more.

＜測定方法＞
［粉体抵抗率の測定方法］
正極集電体１１上の正極活物質層１２をスパチュラで削って得られるサンプルに対して１２０℃、４ｈの真空乾燥を実施したものを測定対象とし、下記の方法で粉体抵抗率を測定した。
日東精工アナリテック社製、粉体抵抗測定システム（型式番号：ＭＣＰ－ＰＤ５１）を用いて測定を実施した。真空乾燥後のサンプルの重量を予め測定した後、半径１０ｍｍの測定セルに投入し、１６ｋＮにて加圧した際の粉体抵抗率（単位Ω・ｃｍ）と、その際の試料厚みを計測した。サンプルの重量と試料厚みの値から測定時の粉体密度（ｇ／ｃｍ３）を求めた。粉体密度は２．０～２．４（ｇ／ｃｍ３）の範囲であり、粉体密度の違いによる測定結果への影響は、無視できる程度に小さいことを確認した。
なお、本例において加圧力は１６ｋＮで一定としたが、これに限らない。測定時の粉体密度は正極活物質層１２に含まれる正極活物質、導電助剤、結着材の含有量により影響を受けるため特に範囲が限定されるものではない。測定ばらつきの影響を避けるため、測定時の粉体密度は２．０～２．４ｇ／ｃｍ３の範囲であることが望ましい。 <Measurement method>
[Method for measuring powder resistivity]
A sample obtained by scraping the positive electrode active material layer 12 on the positive electrode current collector 11 with a spatula was subjected to vacuum drying at 120° C. for 4 hours, and the powder resistivity was measured by the following method. .
Measurement was performed using a powder resistance measurement system (model number: MCP-PD51) manufactured by Nitto Seiko Analyticc. After measuring the weight of the sample after vacuum drying in advance, it was put into a measuring cell with a radius of 10 mm, and the powder resistivity (unit: Ω cm) when pressurized at 16 kN and the sample thickness at that time were measured. . The powder density (g/cm 3 ) at the time of measurement was determined from the sample weight and sample thickness. The powder density was in the range of 2.0 to 2.4 (g/cm 3 ), and it was confirmed that the influence of the difference in powder density on the measurement results was negligibly small.
In this example, the pressurizing force is constant at 16 kN, but it is not limited to this. The powder density at the time of measurement is affected by the contents of the positive electrode active material, the conductive aid, and the binder contained in the positive electrode active material layer 12, so the range is not particularly limited. In order to avoid the influence of measurement variations, the powder density during measurement is preferably in the range of 2.0 to 2.4 g/cm 3 .

［正極活物質層（又は負極活物質層）の単位面積あたりの質量の測定方法］
正極シート（又は負極シート）を、直径１６ｍｍの円形に打ち抜いた測定試料を５枚準備した。
各測定試料の質量を精密天秤にて秤量し、測定結果から、予め測定した正極集電体１１（又は負極集電体３１）の質量を差し引くことにより、測定試料中の正極活物質層（又は負極活物質層）の質量を算出した。
正極活物質層の質量の平均値（単位：ｍｇ）／測定試料の面積（単位：ｃｍ２）により、正極活物質層の単位面積あたりの質量（単位：ｍｇ／ｃｍ２）を求めた。
負極活物質層の質量の平均値（単位：ｍｇ）／測定試料の面積（単位：ｃｍ２）により、負極活物質層の単位面積あたりの質量（単位：ｍｇ／ｃｍ２）を求めた。 [Method for measuring mass per unit area of positive electrode active material layer (or negative electrode active material layer)]
Five measurement samples were prepared by punching a positive electrode sheet (or negative electrode sheet) into a circle with a diameter of 16 mm.
The mass of each measurement sample is weighed with a precision balance, and the mass of the positive electrode current collector 11 (or negative electrode current collector 31) measured in advance is subtracted from the measurement result to obtain the positive electrode active material layer (or The mass of the negative electrode active material layer) was calculated.
The mass per unit area of the positive electrode active material layer (unit: mg/cm 2 ) was obtained from the average value of the mass of the positive electrode active material layer (unit: mg)/the area of the measurement sample (unit: cm 2 ).
The mass per unit area of the negative electrode active material layer (unit: mg/cm 2 ) was obtained from the average value of the mass of the negative electrode active material layer (unit: mg)/the area of the measurement sample (unit: cm 2 ).

＜評価方法＞
［剥離強度の測定方法］
正極活物質層１２の剥離強度は、オートグラフを用いて以下の方法により測定することができる。図６は、正極活物質層の剥離強度の測定方法の工程図である。図６に示す工程（Ｓ１）～（Ｓ７）を順に説明する。図６は、その構成をわかりやすく説明するための模式図であり、各構成要素の寸法比率等は、実際とは異なる場合もある。
（Ｓ１）先ず、幅２５ｍｍ、長さ１２０ｍｍの長方形の両面テープ５０を準備する。両面テープ５０は粘着層５０ａの両面に剥離紙５０ｂ、５０ｃが積層されている。両面テープ５０としては、日東電工社製品名「Ｎｏ．５０１５、２５ｍｍ幅」を用いた。
（Ｓ２）両面テープ５０の片面の離型紙５０ｃを剥がし、粘着層５０ａの表面（以下、「糊面」ともいう。）が露出した粘着体５５とする。粘着体５５において、長さ方向の一端部５５ａからの距離が約１０ｍｍのところに折り曲げ位置５１を設ける。
（Ｓ３）前記折り曲げ位置５１より一端部５５ａ側を、糊面と糊面とが接着するように折り曲げる。
（Ｓ４）粘着体５５の糊面と、正極シート６０の正極活物質層１２とが接触するように、粘着体５５と正極シート６０とを貼り合わせる。
（Ｓ５）粘着体５５の外縁に沿って正極シート６０を切り出し、長さ方向に圧着ローラーを２往復させる方法で、粘着体５５と正極シート６０とを圧着させて複合体６５を得る。
（Ｓ６）ステンレス板７０の一面に、複合体６５の粘着体５５側の外面を接触させ、折り曲げ位置５１とは反対側の他端部６５ｂを、メンディングテープ８０でステンレス板７０に固定する。メンディングテープ８０としては、３Ｍ社製品名「スコッチテープメンディングテープ１８ｍｍ×３０小巻８１０－１－１８Ｄ」を用いた。メンディングテープ８０の長さは約３０ｍｍとし、ステンレス板７０の端部から複合体６５の他端部６５ｂまでの距離Ａは約５ｍｍ、メンディングテープ８０の一端部８０ａから複合体６５の他端部６５ｂまでの距離Ｂは５ｍｍとする。メンディングテープ８０の他端部８０ｂはステンレス板７０の他面に貼り付ける。
（Ｓ７）複合体６５の折り曲げ位置５１側の端部において、粘着体５５から正極シート６０を、長さ方向に対して平行にゆっくりと剥がす。メンディングテープ８０で固定されていない正極シート６０の端部（以下、「剥離端」という）６０ａが、ステンレス板７０からはみ出す程度までゆっくりと剥がす。
次いで、複合体６５が固定されたステンレス板７０を、図示しない引っ張り試験機（島津製作所製品名「ＥＺ－ＬＸ」）に設置し、粘着体５５の折り曲げ位置５１側の端部を固定し、正極シート６０の剥離端６０ａを折り曲げ位置５１とは反対方向（折り曲げ位置５１に対して１８０°方向）に、引っ張り速度６０ｍｍ／分、試験力５００００ｍＮ、ストローク７０ｍｍで引っ張って剥離強度を測定する。ストローク２０～５０ｍｍにおける剥離強度の平均値を、正極活物質層１２の剥離強度とする。 <Evaluation method>
[Method for measuring peel strength]
The peel strength of the positive electrode active material layer 12 can be measured by the following method using an autograph. FIG. 6 is a process diagram of a method for measuring the peel strength of the positive electrode active material layer. Steps (S1) to (S7) shown in FIG. 6 will be described in order. FIG. 6 is a schematic diagram for explaining the configuration in an easy-to-understand manner, and the dimensional ratio of each component may differ from the actual one.
(S1) First, a rectangular double-sided tape 50 having a width of 25 mm and a length of 120 mm is prepared. The double-sided tape 50 has release papers 50b and 50c laminated on both sides of an adhesive layer 50a. As the double-sided tape 50, Nitto Denko's product name "No. 5015, 25 mm width" was used.
(S2) The release paper 50c on one side of the double-sided tape 50 is peeled off to form an adhesive body 55 in which the surface of the adhesive layer 50a (hereinafter also referred to as "adhesive surface") is exposed. The adhesive body 55 is provided with a bending position 51 at a distance of about 10 mm from one longitudinal end 55a.
(S3) The one end portion 55a side from the bending position 51 is folded so that the adhesive surfaces are adhered to each other.
(S4) The adhesive body 55 and the positive electrode sheet 60 are pasted together so that the adhesive surface of the adhesive body 55 and the positive electrode active material layer 12 of the positive electrode sheet 60 are in contact with each other.
(S5) The positive electrode sheet 60 is cut out along the outer edge of the adhesive body 55, and the adhesive body 55 and the positive electrode sheet 60 are press-bonded to obtain a composite body 65 by reciprocating a pressing roller twice in the length direction.
(S6) The outer surface of the adhesive 55 side of the composite 65 is brought into contact with one surface of the stainless steel plate 70, and the other end 65b opposite to the bending position 51 is fixed to the stainless steel plate 70 with the mending tape 80. As the mending tape 80, 3M's product name "Scotch tape mending tape 18 mm×30 small roll 810-1-18D" was used. The length of the mending tape 80 is approximately 30 mm, the distance A from the end of the stainless steel plate 70 to the other end 65b of the composite 65 is approximately 5 mm, and the length of the mending tape 80 is approximately 5 mm. A distance B to the portion 65b is set to 5 mm. The other end 80b of the mending tape 80 is attached to the other surface of the stainless steel plate 70. As shown in FIG.
(S7) Slowly peel the positive electrode sheet 60 from the adhesive body 55 parallel to the length direction at the end of the composite 65 on the bending position 51 side. The edge 60 a of the positive electrode sheet 60 that is not fixed by the mending tape 80 (hereinafter referred to as “peeled edge”) is slowly peeled off to such an extent that it protrudes from the stainless steel plate 70 .
Next, the stainless steel plate 70 to which the composite 65 is fixed is set in a tensile tester (Shimadzu Corporation product name “EZ-LX”) not shown, the end of the adhesive 55 on the bending position 51 side is fixed, and the positive electrode The peel strength is measured by pulling the peeled edge 60a of the sheet 60 in the direction opposite to the bending position 51 (180° direction with respect to the bending position 51) at a pulling speed of 60 mm/min, a test force of 50000 mN, and a stroke of 70 mm. The peel strength of the positive electrode active material layer 12 is the average value of the peel strength at strokes of 20 to 50 mm.

［重量エネルギー密度の測定方法］
重量エネルギー密度の評価は、下記（１）～（３）の手順に沿って行った。
（１）定格容量が１Ａｈとなるようにセルを作製し、セルの重量を測定した。
（２）得られたセルに対して、２５℃（常温）環境下で０．２Ｃレート（すなわち、２００ｍＡ）で一定電流にて終止電圧３．６Ｖで充電を行った後、一定電圧にて前記充電電流の１／１０を終止電流（すなわち、２０ｍＡ）として充電を行った後に３０分間、開回路状態で休止した。
（３）放電を０．２Ｃレートで一定電流にて終止電圧２．５Ｖで行った。このときに放電開始から放電終了までに測定された合計の放電電力（Ｗｈ）を（１）にて測定したセルの重量（ｋｇ）で除する事で重量エネルギー密度（Ｗｈ／ｋｇ）を算出した。 [Method for measuring weight energy density]
The weight energy density was evaluated according to the following procedures (1) to (3).
(1) A cell was produced to have a rated capacity of 1 Ah, and the weight of the cell was measured.
(2) The obtained cell was charged at a constant current of 0.2C rate (i.e., 200mA) under an environment of 25°C (normal temperature) at a final voltage of 3.6V, and then at a constant voltage. After charging with 1/10 of the charging current as the final current (ie, 20 mA), the battery was rested in an open circuit state for 30 minutes.
(3) Discharge was performed at a constant current of 0.2C rate and a final voltage of 2.5V. At this time, the weight energy density (Wh/kg) was calculated by dividing the total discharge power (Wh) measured from the start of discharge to the end of discharge by the weight (kg) of the cell measured in (1). .

［インピーダンスの測定方法］
定格容量が１Ａｈとなるようにセルを作製し、得られたセルに対して、２５℃（常温）環境下で０．２Ｃレート（すなわち、２００ｍＡ）で一定電流にて終止電圧３．６Ｖで充電を行った後、一定電圧にて前記充電電流の１／１０を終止電流（すなわち、２０ｍＡ）として充電を行った後に、常温（２５℃）、周波数０．１ｋＨｚの条件でインピーダンスを測定した。
測定は正負極タブにそれぞれ電流端子、電圧端子を取り付ける４端子法にて実施した。測定には一例として、ＢｉｏＬｏｇｉｃ社製インピーダンスアナライザを用いた。 [Method of measuring impedance]
A cell is produced so that the rated capacity is 1 Ah, and the obtained cell is charged at a constant current of 0.2 C rate (i.e., 200 mA) at a final voltage of 3.6 V in a 25 ° C. (room temperature) environment. After that, the battery was charged at a constant voltage with 1/10 of the charging current as the terminal current (that is, 20 mA), and then the impedance was measured at room temperature (25° C.) and a frequency of 0.1 kHz.
The measurement was performed by a four-terminal method in which a current terminal and a voltage terminal are attached to the positive and negative tabs, respectively. As an example, an impedance analyzer manufactured by BioLogic was used for the measurement.

＜例Ｃ１～Ｃ８＞
例Ｃ１～Ｃ５は実施例、例Ｃ６～Ｃ８は比較例である。
正極活物質として、炭素で被覆されたリン酸鉄リチウム（以下「カーボンコート活物質」ともいう、平均粒子径１．０μｍ、炭素含有量１質量％）を用いた。
導電助剤としてカーボンブラックを用いた。
結着材としてポリフッ化ビニリデン（ＰＶＤＦ）を用いた。 <Examples C1 to C8>
Examples C1-C5 are working examples, and examples C6-C8 are comparative examples.
As the positive electrode active material, carbon-coated lithium iron phosphate (hereinafter also referred to as “carbon-coated active material”, average particle diameter of 1.0 μm, carbon content of 1% by mass) was used.
Carbon black was used as a conductive aid.
Polyvinylidene fluoride (PVDF) was used as a binder.

［例Ｃ１］
まず、以下の方法で正極集電体本体１４の表裏両面を集電体被覆層１５で被覆して正極集電体１１を作製した。正極集電体本体１４としてはアルミニウム箔（厚さ１５μｍ）を用いた。
カーボンブラック１００質量部と、結着材であるポリフッ化ビニリデン４０質量部と、溶媒であるＮ－メチルピロリドン（ＮＭＰ）とを混合してスラリーを得た。ＮＭＰの使用量はスラリーを塗工するのに必要な量とした。
得られたスラリーを正極集電体本体１４の両面に、乾燥後の集電体被覆層１５の厚さ（両面合計）が２μｍとなるように、グラビア法で塗工し、乾燥し溶媒を除去して正極集電体１１とした。両面それぞれの集電体被覆層１５は、塗工量及び厚みが互いに均等になるように形成した。 [Example C1]
First, the positive electrode current collector 11 was produced by coating the front and back surfaces of the positive electrode current collector body 14 with the current collector coating layer 15 by the following method. An aluminum foil (thickness: 15 μm) was used as the positive electrode current collector main body 14 .
A slurry was obtained by mixing 100 parts by mass of carbon black, 40 parts by mass of polyvinylidene fluoride as a binder, and N-methylpyrrolidone (NMP) as a solvent. The amount of NMP used was the amount necessary for coating the slurry.
The obtained slurry is applied to both surfaces of the positive electrode current collector main body 14 by a gravure method so that the thickness of the current collector coating layer 15 after drying (both sides total) is 2 μm, and dried to remove the solvent. Then, the positive electrode current collector 11 was obtained. The current collector coating layers 15 on both sides were formed so that the coating amount and thickness were uniform.

次いで、以下の方法で正極活物質層１２を形成した。
表４に示す配合で、正極活物質と、導電助剤と、結着材と、溶媒（ＮＭＰ）とを、ミキサーにて混合して正極製造用組成物を得た。溶媒の使用量は、正極製造用組成物を塗工するのに必要な量とした。
正極集電体１１の両面上に、それぞれ正極製造用組成物を塗工し、予備乾燥後、１２０℃環境で真空乾燥して正極活物質層１２を形成した。正極製造用組成物の塗工量を表５に示す（以下、同様）。得られた積層物を１０ｋＮの荷重で加圧プレスして正極シートを得た。両面それぞれの正極活物質層１２は、塗工量及び厚みが互いに均等になるように形成した。
得られた正極シートを試料として、粉体抵抗率、結着材含有量、正極活物質層の単位面積あたりの質量、及び剥離強度を測定した。
カーボンコート活物質の炭素含有量と配合量、及び導電助剤の炭素含有量と配合量に基づいて、正極活物質層の総質量に対する導電性炭素の含有量を算出した。導電助剤は、不純物が定量限界以下であり、炭素含有量１００質量％とみなした。正極活物質層の総質量に対する導電性炭素の含有量は上記≪導電性炭素含有量の測定方法≫に記載の方法を用いて確認することも可能である。これらの結果を表５に示す（以下、同様）。
得られた正極シートを打ち抜き、正極とした。 Next, the positive electrode active material layer 12 was formed by the following method.
A positive electrode active material, a conductive aid, a binder, and a solvent (NMP) were mixed in a mixer according to the formulation shown in Table 4 to obtain a positive electrode manufacturing composition. The amount of the solvent used was the amount necessary for coating the composition for manufacturing a positive electrode.
On both sides of the positive electrode current collector 11 , the positive electrode manufacturing composition was applied, pre-dried, and then vacuum dried in an environment of 120° C. to form the positive electrode active material layer 12 . Table 5 shows the coating amount of the positive electrode-manufacturing composition (the same applies hereinafter). The resulting laminate was pressed under a load of 10 kN to obtain a positive electrode sheet. The positive electrode active material layers 12 on both sides were formed so that the coating amount and thickness were uniform.
Using the obtained positive electrode sheet as a sample, the powder resistivity, binder content, mass per unit area of the positive electrode active material layer, and peel strength were measured.
Based on the carbon content and compounding amount of the carbon-coated active material and the carbon content and compounding amount of the conductive aid, the content of conductive carbon with respect to the total mass of the positive electrode active material layer was calculated. The conductivity aid contained impurities below the quantitative limit and was considered to have a carbon content of 100% by mass. The content of conductive carbon with respect to the total mass of the positive electrode active material layer can also be confirmed by using the method described in <<Method for Measuring Content of Conductive Carbon>> above. These results are shown in Table 5 (hereinafter the same).
The obtained positive electrode sheet was punched out to obtain a positive electrode.

以下の方法で、図２に示す構成の非水電解質二次電池を製造した。
エチレンカーボネート（ＥＣ）とジエチルカーボネート（ＤＥＣ）を、ＥＣ：ＤＥＣの体積比が３：７となるように混合した溶媒に、電解質としてＬｉＰＦ６を１モル／リットルとなるように溶解して、非水電解液を調製した。
本例で得た正極と、製造例１で得た負極とを、セパレータを介して交互に積層し、最外層が負極である電極積層体を作製した。セパレータとしては、ポリオレフィンフィルム（厚さ１５μｍ）を用いた。
電極積層体を作製する工程では、まず、セパレータ２と正極１とを積層し、その後、セパレータ２上に負極３を積層した。
電極積層体の正極集電体露出部１３及び負極集電体露出部３３のそれぞれに、端子用タブを電気的に接続し、端子用タブが外部に突出するように、アルミラミネートフィルムで電極積層体を挟み、三辺をラミネート加工して封止した。
続いて、封止せずに残した一辺から非水電解液を注入し、真空封止して非水電解質二次電池（ラミネートセル）を製造した。
上記の方法で、重量エネルギー密度及びインピーダンスを測定した。結果を表５に示す（以下、同様）。 A non-aqueous electrolyte secondary battery having the configuration shown in FIG. 2 was manufactured by the following method.
Ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed so that the volume ratio of EC:DEC was 3:7. An aqueous electrolyte was prepared.
The positive electrode obtained in this example and the negative electrode obtained in Production Example 1 were alternately laminated via a separator to prepare an electrode laminate having the negative electrode as the outermost layer. A polyolefin film (thickness: 15 μm) was used as the separator.
In the process of producing the electrode laminate, first, the separator 2 and the positive electrode 1 were laminated, and then the negative electrode 3 was laminated on the separator 2 .
A terminal tab is electrically connected to each of the positive electrode current collector exposed portion 13 and the negative electrode current collector exposed portion 33 of the electrode laminate, and the electrodes are stacked with an aluminum laminate film so that the terminal tab protrudes to the outside. The body was sandwiched, and three sides were laminated and sealed.
Subsequently, a non-aqueous electrolyte was injected from one side that was left unsealed, and vacuum-sealed to manufacture a non-aqueous electrolyte secondary battery (laminate cell).
Gravimetric energy density and impedance were measured by the methods described above. The results are shown in Table 5 (same below).

［例Ｃ２］
例Ｃ１において、正極活物質層の単位面積あたりの質量が表５に示す値となるように、正極製造用組成物の塗工量を変更した。それ以外は例Ｃ１と同様にして正極を作製した。
製造例１において、負極活物質層の単位面積あたりの質量が表５に示す値となるように、負極製造用組成物の塗工量を変更した負極を用いた。それ以外は例Ｃ１と同様にして二次電池を製造して評価した。 [Example C2]
In Example C1, the coating amount of the composition for manufacturing a positive electrode was changed so that the mass per unit area of the positive electrode active material layer was the value shown in Table 5. Otherwise, a positive electrode was produced in the same manner as in Example C1.
In Production Example 1, the negative electrode was used in which the coating amount of the negative electrode-manufacturing composition was changed so that the mass per unit area of the negative electrode active material layer was the value shown in Table 5. Otherwise, a secondary battery was produced and evaluated in the same manner as in Example C1.

［例Ｃ３］
例Ｃ２において、正極製造用組成物の配合を表４に示すとおりに変更した。それ以外は例Ｃ２と同様にして正極を作製し、二次電池を製造して評価した。 [Example C3]
In Example C2, the formulation of the positive electrode manufacturing composition was changed as shown in Table 4. Otherwise, a positive electrode was produced in the same manner as in Example C2, and a secondary battery was produced and evaluated.

［例Ｃ４］
例Ｃ３において、正極活物質層の単位面積あたりの質量が表５に示す値となるように、正極製造用組成物の塗工量を変更した。それ以外は例Ｃ３と同様にして正極を作製した。
製造例１において、負極活物質層の単位面積あたりの質量が表５に示す値となるように、負極製造用組成物の塗工量を変更した負極を用いた。それ以外は例Ｃ３と同様にして二次電池を製造して評価した。 [Example C4]
In Example C3, the coating amount of the composition for manufacturing a positive electrode was changed so that the mass per unit area of the positive electrode active material layer was the value shown in Table 5. Otherwise, a positive electrode was produced in the same manner as in Example C3.
In Production Example 1, the negative electrode was used in which the coating amount of the negative electrode-manufacturing composition was changed so that the mass per unit area of the negative electrode active material layer was the value shown in Table 5. Otherwise, a secondary battery was produced and evaluated in the same manner as in Example C3.

［例Ｃ５］
例Ｃ１において、正極製造用組成物の配合を表４に示すとおりに変更した。正極活物質層の単位面積当たりの質量が表５に示す値となるように、正極製造用組成物の塗工量を変更した。負極活物質層の単位面積あたりの質量が表５に示す値となるように、負極製造用組成物の塗工量を変更した負極を用いた。それ以外は例Ｃ１と同様にして正極を作製し、二次電池を製造して評価した。 [Example C5]
In Example C1, the formulation of the positive electrode manufacturing composition was changed as shown in Table 4. The coating amount of the positive electrode manufacturing composition was changed so that the mass per unit area of the positive electrode active material layer was the value shown in Table 5. A negative electrode in which the coating amount of the composition for manufacturing a negative electrode was changed so that the mass per unit area of the negative electrode active material layer was the value shown in Table 5 was used. Otherwise, a positive electrode was produced in the same manner as in Example C1, and a secondary battery was produced and evaluated.

［例Ｃ６、Ｃ７］
例Ｃ１において、正極製造用組成物の配合を表４に示すとおりに変更した。それ以外は例Ｃ１と同様にして正極を作製し、二次電池を製造して評価した。 [Example C6, C7]
In Example C1, the formulation of the positive electrode manufacturing composition was changed as shown in Table 4. Otherwise, a positive electrode was produced in the same manner as in Example C1, and a secondary battery was produced and evaluated.

［例Ｃ８］
例Ｃ２において、正極製造用組成物の配合を表４に示すとおりに変更した。それ以外は例Ｃ２と同様にして正極を作製し、二次電池を製造して評価した。 [Example C8]
In Example C2, the formulation of the positive electrode manufacturing composition was changed as shown in Table 4. Otherwise, a positive electrode was produced in the same manner as in Example C2, and a secondary battery was produced and evaluated.

Figure 2023024425000005
Figure 2023024425000005

Figure 2023024425000006
Figure 2023024425000006

表５の結果に示されるように、正極活物質層の粉体抵抗率が１０～１，０００Ω・ｃｍである例Ｃ１～Ｃ５は、正極活物質層の剥離強度が良好であり、非水電解質二次電池のインピーダンスが低く、重量エネルギー密度が高かった。 As shown in Table 5, in Examples C1 to C5 in which the positive electrode active material layer had a powder resistivity of 10 to 1,000 Ω cm, the peel strength of the positive electrode active material layer was good, and the non-aqueous electrolyte The impedance of the secondary battery was low and the weight energy density was high.

例Ｃ１は、充分な剥離強度が得られる範囲で結着材の含有量を減らした例である。例Ｃ５と比べて、正極活物質層の粉体抵抗率が高いにもかかわらず、非水電解質二次電池のインピーダンスが低下し、重量エネルギー密度が増大した。
例Ｃ２は、例Ｃ１より正極製造用組成物の塗工量を増やした結果、良好な剥離強度を担保しつつ、重量エネルギー密度がさらに増大した。
例Ｃ３は、例Ｃ２より結着材の含有量が若干多く、剥離強度が向上した。結着材の増量による粉体抵抗率及びインピーダンスの上昇は小さく、良好な特性が得られた。
例Ｃ４は、例Ｃ３より正極製造用組成物の塗工量を増やした結果、良好な剥離強度を担保しつつ、重量エネルギー密度がさらに増大した。
例Ｃ５では、導電助剤を使用しなかったが、粉体抵抗率及びインピーダンスの上昇は小さく、良好な特性が得られた。良好な剥離強度を担保しつつ、重量エネルギー密度が最も高くなった。 Example C1 is an example in which the content of the binder is reduced to the extent that sufficient peel strength is obtained. Although the powder resistivity of the positive electrode active material layer was higher than in Example C5, the impedance of the non-aqueous electrolyte secondary battery was lowered and the weight energy density was increased.
In Example C2, as a result of increasing the coating amount of the composition for manufacturing a positive electrode from Example C1, the weight energy density was further increased while ensuring good peel strength.
Example C3 had a slightly higher binder content than Example C2 and improved peel strength. An increase in powder resistivity and impedance due to an increase in the amount of binder was small, and good characteristics were obtained.
In Example C4, as a result of increasing the coating amount of the composition for manufacturing a positive electrode from Example C3, the weight energy density was further increased while ensuring good peel strength.
In Example C5, no conductivity aid was used, but the increase in powder resistivity and impedance was small, and good characteristics were obtained. The weight energy density was the highest while ensuring good peel strength.

例Ｃ６は、例Ｃ１に比べて導電助剤及び結着材の含有量が多く、正極活物質層の粉体抵抗率が低い。剥離強度は例Ｃ１と同等であるが、非水電解質二次電池のインピーダンスが高く、重量エネルギー密度が低かった。
例Ｃ７は、例Ｃ６より結着材の含有量を減らした結果、剥離強度が劣った。
例Ｃ８は、例Ｃ６より正極製造用組成物の塗工量を増やした例である。正極活物質層の単位面積あたりの質量は例Ｃ２と同じであるが、例Ｃ２に比べて導電助剤及び結着材の含有量が多く、正極活物質層の粉体抵抗率が低い。例Ｃ２より非水電解質二次電池のインピーダンスが高く、重量エネルギー密度が低かった。 In Example C6, the contents of the conductive aid and the binder are higher than in Example C1, and the powder resistivity of the positive electrode active material layer is lower. Although the peel strength was equivalent to that of Example C1, the impedance of the non-aqueous electrolyte secondary battery was high and the weight energy density was low.
Example C7 was inferior to Example C6 in peel strength as a result of reducing the binder content.
Example C8 is an example in which the coating amount of the composition for manufacturing a positive electrode is increased from that of Example C6. Although the mass per unit area of the positive electrode active material layer is the same as in Example C2, the contents of the conductive aid and the binder are higher than in Example C2, and the powder resistivity of the positive electrode active material layer is lower. The impedance of the non-aqueous electrolyte secondary battery was higher than that of Example C2, and the weight energy density was lower.

１ 正極
２ セパレータ
３ 負極
５ 外装体
１０ 二次電池
１１ 正極集電体
１２ 正極活物質層
１３ 正極集電体露出部
１４ 正極集電体本体
１５ 集電体被覆層
３１ 負極集電体
３２ 負極活物質層
３３ 負極集電体露出部
５０ 両面テープ
５０ａ 粘着層
５０ｂ 剥離紙
５１ 折り曲げ位置
５５ 粘着体
６０ 正極シート
７０ ステンレス板
８０ メンディングテープ REFERENCE SIGNS LIST 1 positive electrode 2 separator 3 negative electrode 5 exterior body 10 secondary battery 11 positive electrode current collector 12 positive electrode active material layer 13 positive electrode current collector exposed portion 14 positive electrode current collector body 15 current collector coating layer 31 negative electrode current collector 32 negative electrode active Substance layer 33 Negative electrode current collector exposed portion 50 Double-sided tape 50a Adhesive layer 50b Release paper 51 Folding position 55 Adhesive body 60 Positive electrode sheet 70 Stainless steel plate 80 Mending tape

Claims (34)

集電体と、前記集電体上に存在する、正極活物質粒子を含む正極活物質層を有し、
前記正極活物質層の拡がり抵抗値分布において、抵抗値４．０～１２．５（ｌｏｇΩ）の頻度合計を１００％とするとき、抵抗値４．０～６．０（ｌｏｇΩ）の頻度合計が０．０～５．０％である、非水電解質二次電池用正極。 having a current collector and a positive electrode active material layer containing positive electrode active material particles present on the current collector;
In the spreading resistance value distribution of the positive electrode active material layer, when the total frequency of resistance values 4.0 to 12.5 (log Ω) is 100%, the total frequency of resistance values 4.0 to 6.0 (log Ω) is A positive electrode for a non-aqueous electrolyte secondary battery, which is 0.0 to 5.0%. 前記拡がり抵抗値分布において、抵抗値４．０～６．０（ｌｏｇΩ）の平均頻度より、抵抗値６．０～９．０（ｌｏｇΩ）の平均頻度が大きい、請求項１に記載の非水電解質二次電池用正極。 2. The nonaqueous according to claim 1, wherein in the spreading resistance value distribution, the average frequency of resistance values 6.0 to 9.0 (log Ω) is higher than the average frequency of resistance values 4.0 to 6.0 (log Ω). Positive electrode for electrolyte secondary batteries. 前記正極活物質層が導電助剤を含む、請求項１又は２に記載の非水電解質二次電池用正極。 3. The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein said positive electrode active material layer contains a conductive aid. 前記正極活物質粒子の表面の少なくとも一部に、導電材料を含む活物質被覆部が存在する、請求項３に記載の非水電解質二次電池用正極。 4. The positive electrode for a non-aqueous electrolyte secondary battery according to claim 3, wherein an active material coating portion containing a conductive material is present on at least part of the surface of said positive electrode active material particles. 前記正極活物質層が導電助剤を含まず、前記正極活物質粒子の表面の少なくとも一部に、導電材料を含む活物質被覆部が存在する、請求項１又は２に記載の非水電解質二次電池用正極。 3. The non-aqueous electrolyte 2 according to claim 1, wherein the positive electrode active material layer does not contain a conductive aid, and an active material coating portion containing a conductive material is present on at least part of the surface of the positive electrode active material particles. Positive electrode for secondary batteries. 前記正極活物質層が導電性炭素を含み、前記正極活物質層の総質量に対して前記導電性炭素の含有量が０．５質量％以上３．０質量％未満である、請求項３～５のいずれか一項に記載の非水電解質二次電池用正極。 Claims 3 to 3, wherein the positive electrode active material layer contains conductive carbon, and the content of the conductive carbon is 0.5% by mass or more and less than 3.0% by mass with respect to the total mass of the positive electrode active material layer. 6. The positive electrode for a non-aqueous electrolyte secondary battery according to any one of 5. 前記正極活物質粒子が、一般式ＬｉＦｅｘＭ（１－ｘ）ＰＯ４（式中、０≦ｘ≦１、ＭはＣｏ、Ｎｉ、Ｍｎ、Ａｌ、Ｔｉ又はＺｒである。）で表される化合物を含む、請求項１～６のいずれか一項に記載の非水電解質二次電池用正極。 The positive electrode active material particles are represented by the general formula LiFe x M (1-x) PO 4 (where 0≦x≦1 and M is Co, Ni, Mn, Al, Ti or Zr). The positive electrode for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 6, comprising a compound. 前記集電体の、前記正極活物質層側の表面の少なくとも一部に、導電材料を含む集電体被覆層が存在する、請求項１～７のいずれか一項に記載の非水電解質二次電池用正極。 The non-aqueous electrolyte 2 according to any one of claims 1 to 7, wherein a current collector coating layer containing a conductive material is present on at least part of the surface of the current collector on the positive electrode active material layer side. Positive electrode for secondary batteries. 請求項１～８のいずれか一項に記載の非水電解質二次電池用正極、負極、及び前記非水電解質二次電池用正極と負極との間に存在する非水電解質を備える、非水電解質二次電池。 The positive electrode for the non-aqueous electrolyte secondary battery according to any one of claims 1 to 8, the negative electrode, and the non-aqueous electrolyte present between the positive electrode and the negative electrode for the non-aqueous electrolyte secondary battery, non-aqueous Electrolyte secondary battery. 請求項９に記載の非水電解質二次電池の複数個を備える、電池モジュール又は電池システム。 A battery module or battery system comprising a plurality of non-aqueous electrolyte secondary batteries according to claim 9 . 集電体と、前記集電体上に存在する正極活物質層を有し、
前記正極活物質層が正極活物質及び導電性炭素材料を含み、
前記正極活物質層の総質量に対して、抵抗率が０．１０Ω・ｃｍ以下である低抵抗導電性炭素材料の含有量が０．５質量％以下である、非水電解質二次電池用正極。 having a current collector and a positive electrode active material layer present on the current collector;
the positive electrode active material layer includes a positive electrode active material and a conductive carbon material;
A positive electrode for a non-aqueous electrolyte secondary battery, wherein the content of a low-resistance conductive carbon material having a resistivity of 0.10 Ω·cm or less is 0.5% by mass or less with respect to the total mass of the positive electrode active material layer. . 前記正極活物質層の総質量に対して、抵抗率が０．０２Ω・ｃｍ以下である低抵抗導電性炭素材料の含有量が０．５質量％以下である、請求項１１に記載の非水電解質二次電池用正極。 The non-aqueous according to claim 11, wherein the content of the low-resistance conductive carbon material having a resistivity of 0.02 Ω·cm or less is 0.5% by mass or less with respect to the total mass of the positive electrode active material layer. Positive electrode for electrolyte secondary batteries. 前記正極活物質層が、前記正極活物質からなる粒子本体と、前記粒子本体の表面の少なくとも一部に存在する活物質被覆部を含み、
前記導電性炭素材料の少なくとも一部が前記活物質被覆部であり、前記活物質被覆部の抵抗率が０．１５Ω・ｃｍ以上である、請求項１１又は１２に記載の非水電解質二次電池用正極。 The positive electrode active material layer includes a particle body made of the positive electrode active material and an active material coating portion present on at least a part of the surface of the particle body,
13. The non-aqueous electrolyte secondary battery according to claim 11, wherein at least part of said conductive carbon material is said active material coating portion, and said active material coating portion has a resistivity of 0.15 Ω·cm or more. positive electrode. 前記正極活物質層の総質量に対して、前記活物質被覆部の含有量が０．９質量％以上である、請求項１３に記載の非水電解質二次電池用正極。 14. The positive electrode for a non-aqueous electrolyte secondary battery in accordance with claim 13, wherein the content of said active material coating portion is 0.9% by mass or more with respect to the total mass of said positive electrode active material layer. 前記正極活物質層が導電助剤を含み、前記導電性炭素材料の少なくとも一部が前記導電助剤である、請求項１１～１４のいずれか一項に記載の非水電解質二次電池用正極。 The positive electrode for a non-aqueous electrolyte secondary battery according to any one of claims 11 to 14, wherein the positive electrode active material layer contains a conductive aid, and at least part of the conductive carbon material is the conductive aid. . 前記正極活物質が、一般式ＬｉＦｅｘＭ（１－ｘ）ＰＯ４（式中、０≦ｘ≦１、ＭはＣｏ、Ｎｉ、Ｍｎ、Ａｌ、Ｔｉ又はＺｒである。）で表される化合物を含む、請求項１１～１５のいずれか一項に記載の非水電解質二次電池用正極。 The positive electrode active material is a compound represented by the general formula LiFe x M (1-x) PO 4 (where 0≦x≦1 and M is Co, Ni, Mn, Al, Ti or Zr). The positive electrode for a non-aqueous electrolyte secondary battery according to any one of claims 11 to 15, comprising 請求項１１～１６のいずれか一項に記載の非水電解質二次電池用正極、負極、及び前記非水電解質二次電池用正極と負極との間に存在する非水電解質を備える、非水電解質二次電池。 The positive electrode for the non-aqueous electrolyte secondary battery according to any one of claims 11 to 16, the negative electrode, and the non-aqueous electrolyte present between the positive electrode and the negative electrode for the non-aqueous electrolyte secondary battery, non-aqueous Electrolyte secondary battery. 請求項１７に記載の非水電解質二次電池の複数個を備える、電池モジュール又は電池システム。 A battery module or battery system comprising a plurality of non-aqueous electrolyte secondary batteries according to claim 17. 正極集電体と、前記正極集電体上に存在する正極活物質層とを有し、
前記正極活物質層が正極活物質を含み、
前記正極活物質の表面の少なくとも一部に、導電材料を含む活物質被覆部が存在し、
前記正極活物質層の粉体抵抗率が１０～１，０００Ω・ｃｍである、非水電解質二次電池用正極。 Having a positive electrode current collector and a positive electrode active material layer present on the positive electrode current collector,
The positive electrode active material layer contains a positive electrode active material,
An active material coating portion containing a conductive material is present on at least part of the surface of the positive electrode active material,
A positive electrode for a non-aqueous electrolyte secondary battery, wherein the positive electrode active material layer has a powder resistivity of 10 to 1,000 Ω·cm. 前記正極活物質層が結着材を含み、
前記正極活物質層の総質量に対して、結着材の含有量が０．１～１．０質量％である、請求項１９に記載の非水電解質二次電池用正極。 The positive electrode active material layer contains a binder,
20. The positive electrode for a non-aqueous electrolyte secondary battery in accordance with claim 19, wherein the content of the binder is 0.1 to 1.0% by mass with respect to the total mass of said positive electrode active material layer. 前記結着材がポリフッ化ビニリデンを含む、請求項２０に記載の非水電解質二次電池用正極。 21. The positive electrode for a non-aqueous electrolyte secondary battery in accordance with claim 20, wherein said binder contains polyvinylidene fluoride. 前記正極活物質層の剥離強度が１０～１，０００ｍＮ／ｃｍである、請求項１９～２１のいずれか一項に記載の非水電解質二次電池用正極。 The positive electrode for a non-aqueous electrolyte secondary battery according to any one of claims 19 to 21, wherein the positive electrode active material layer has a peel strength of 10 to 1,000 mN/cm. 前記正極集電体の両面に前記正極活物質層が存在し、前記両面の正極活物質層の合計の単位面積あたりの質量が２０～１００ｍｇ／ｃｍ２である、請求項１９～２２のいずれか一項に記載の非水電解質二次電池用正極。 Any one of claims 19 to 22, wherein the positive electrode active material layers are present on both sides of the positive electrode current collector, and the total mass per unit area of the positive electrode active material layers on both sides is 20 to 100 mg/cm 2 . The positive electrode for non-aqueous electrolyte secondary batteries according to item 1. 前記正極集電体の、前記正極活物質層側の表面に集電体被覆層が存在する、請求項１９～２３のいずれか一項に記載の非水電解質二次電池用正極。 The positive electrode for a non-aqueous electrolyte secondary battery according to any one of claims 19 to 23, wherein a current collector coating layer is present on the surface of the positive electrode current collector on the positive electrode active material layer side. 前記集電体被覆層が炭素を含む、請求項２４に記載の非水電解質二次電池用正極。 25. The positive electrode for a non-aqueous electrolyte secondary battery in accordance with claim 24, wherein said current collector coating layer contains carbon. 前記導電材料が炭素を含む、請求項１９～２５のいずれか一項に記載の非水電解質二次電池用正極。 The positive electrode for a nonaqueous electrolyte secondary battery according to any one of claims 19 to 25, wherein said conductive material contains carbon. 前記正極活物質が、一般式ＬｉＦｅｘＭ（１－ｘ）ＰＯ４（式中、０≦ｘ≦１、ＭはＣｏ、Ｎｉ、Ｍｎ、Ａｌ、Ｔｉ又はＺｒである。）で表される化合物を含む、請求項１９～２６のいずれか一項に記載の非水電解質二次電池用正極。 The positive electrode active material is a compound represented by the general formula LiFe x M (1-x) PO 4 (where 0≦x≦1 and M is Co, Ni, Mn, Al, Ti or Zr). The positive electrode for a non-aqueous electrolyte secondary battery according to any one of claims 19 to 26, comprising 前記正極活物質が、ＬｉＦｅＰＯ４で表されるリン酸鉄リチウムである、請求項２７に記載の非水電解質二次電池用正極。 28. The positive electrode for a non-aqueous electrolyte secondary battery in accordance with claim 27, wherein said positive electrode active material is lithium iron phosphate represented by LiFePO4 . 前記正極活物質層が、さらに導電助剤を含む、請求項１９～２８のいずれか一項に記載の非水電解質二次電池用正極。 The positive electrode for a non-aqueous electrolyte secondary battery according to any one of claims 19 to 28, wherein said positive electrode active material layer further contains a conductive aid. 前記導電助剤が炭素を含む、請求項２９に記載の非水電解質二次電池用正極。 30. The positive electrode for a non-aqueous electrolyte secondary battery in accordance with claim 29, wherein said conductive aid contains carbon. 前記正極活物質層が導電助剤を含まない、請求項１９～２８のいずれか一項に記載の非水電解質二次電池用正極。 The positive electrode for a non-aqueous electrolyte secondary battery according to any one of claims 19 to 28, wherein said positive electrode active material layer does not contain a conductive aid. 請求項１９～３１のいずれか一項に記載の非水電解質二次電池用正極、負極、及び前記非水電解質二次電池用正極と負極との間に存在する非水電解質を備える、非水電解質二次電池。 The positive electrode for the non-aqueous electrolyte secondary battery according to any one of claims 19 to 31, the negative electrode, and the non-aqueous electrolyte present between the positive electrode and the negative electrode for the non-aqueous electrolyte secondary battery, non-aqueous Electrolyte secondary battery. 重量エネルギー密度が１２０Ｗｈ／ｋｇ以上である、請求項３２に記載の非水電解質二次電池。 33. The non-aqueous electrolyte secondary battery according to claim 32, having a weight energy density of 120 Wh/kg or more. 請求項３２又は３３に記載の非水電解質二次電池の複数個を備える、電池モジュール又は電池システム。 A battery module or battery system comprising a plurality of non-aqueous electrolyte secondary batteries according to claim 32 or 33.
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